… | |
… | |
58 | |
58 | |
59 | =head2 TYPES / TYPE SUPPORT |
59 | =head2 TYPES / TYPE SUPPORT |
60 | |
60 | |
61 | ecb.h makes sure that the following types are defined (in the expected way): |
61 | ecb.h makes sure that the following types are defined (in the expected way): |
62 | |
62 | |
63 | int8_t uint8_t int16_t uint16_t |
63 | int8_t uint8_ |
64 | int32_t uint32_t int64_t uint64_t |
64 | int16_t uint16_t |
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65 | int32_t uint32_ |
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66 | int64_t uint64_t |
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67 | int_fast8_t uint_fast8_t |
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68 | int_fast16_t uint_fast16_t |
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69 | int_fast32_t uint_fast32_t |
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70 | int_fast64_t uint_fast64_t |
65 | intptr_t uintptr_t |
71 | intptr_t uintptr_t |
66 | |
72 | |
67 | The macro C<ECB_PTRSIZE> is defined to the size of a pointer on this |
73 | The macro C<ECB_PTRSIZE> is defined to the size of a pointer on this |
68 | platform (currently C<4> or C<8>) and can be used in preprocessor |
74 | platform (currently C<4> or C<8>) and can be used in preprocessor |
69 | expressions. |
75 | expressions. |
70 | |
76 | |
71 | For C<ptrdiff_t> and C<size_t> use C<stddef.h>. |
77 | For C<ptrdiff_t> and C<size_t> use C<stddef.h>/C<cstddef>. |
72 | |
78 | |
73 | =head2 LANGUAGE/COMPILER VERSIONS |
79 | =head2 LANGUAGE/ENVIRONMENT/COMPILER VERSIONS |
74 | |
80 | |
75 | All the following symbols expand to an expression that can be tested in |
81 | All the following symbols expand to an expression that can be tested in |
76 | preprocessor instructions as well as treated as a boolean (use C<!!> to |
82 | preprocessor instructions as well as treated as a boolean (use C<!!> to |
77 | ensure it's either C<0> or C<1> if you need that). |
83 | ensure it's either C<0> or C<1> if you need that). |
78 | |
84 | |
79 | =over 4 |
85 | =over 4 |
80 | |
86 | |
81 | =item ECB_C |
87 | =item ECB_C |
82 | |
88 | |
83 | True if the implementation defines the C<__STDC__> macro to a true value, |
89 | True if the implementation defines the C<__STDC__> macro to a true value, |
84 | while not claiming to be C++. |
90 | while not claiming to be C++, i..e C, but not C++. |
85 | |
91 | |
86 | =item ECB_C99 |
92 | =item ECB_C99 |
87 | |
93 | |
88 | True if the implementation claims to be compliant to C99 (ISO/IEC |
94 | True if the implementation claims to be compliant to C99 (ISO/IEC |
89 | 9899:1999) or any later version, while not claiming to be C++. |
95 | 9899:1999) or any later version, while not claiming to be C++. |
90 | |
96 | |
91 | Note that later versions (ECB_C11) remove core features again (for |
97 | Note that later versions (ECB_C11) remove core features again (for |
92 | example, variable length arrays). |
98 | example, variable length arrays). |
93 | |
99 | |
94 | =item ECB_C11 |
100 | =item ECB_C11, ECB_C17 |
95 | |
101 | |
96 | True if the implementation claims to be compliant to C11 (ISO/IEC |
102 | True if the implementation claims to be compliant to C11/C17 (ISO/IEC |
97 | 9899:2011) or any later version, while not claiming to be C++. |
103 | 9899:2011, :20187) or any later version, while not claiming to be C++. |
98 | |
104 | |
99 | =item ECB_CPP |
105 | =item ECB_CPP |
100 | |
106 | |
101 | True if the implementation defines the C<__cplusplus__> macro to a true |
107 | True if the implementation defines the C<__cplusplus__> macro to a true |
102 | value, which is typically true for C++ compilers. |
108 | value, which is typically true for C++ compilers. |
103 | |
109 | |
104 | =item ECB_CPP11 |
110 | =item ECB_CPP11, ECB_CPP14, ECB_CPP17 |
105 | |
111 | |
106 | True if the implementation claims to be compliant to ISO/IEC 14882:2011 |
112 | True if the implementation claims to be compliant to C++11/C++14/C++17 |
107 | (C++11) or any later version. |
113 | (ISO/IEC 14882:2011, :2014, :2017) or any later version. |
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114 | |
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115 | Note that many C++20 features will likely have their own feature test |
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116 | macros (see e.g. L<http://eel.is/c++draft/cpp.predefined#1.8>). |
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117 | |
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118 | =item ECB_OPTIMIZE_SIZE |
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119 | |
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120 | Is C<1> when the compiler optimizes for size, C<0> otherwise. This symbol |
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121 | can also be defined before including F<ecb.h>, in which case it will be |
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122 | unchanged. |
108 | |
123 | |
109 | =item ECB_GCC_VERSION (major, minor) |
124 | =item ECB_GCC_VERSION (major, minor) |
110 | |
125 | |
111 | Expands to a true value (suitable for testing in by the preprocessor) |
126 | Expands to a true value (suitable for testing by the preprocessor) if the |
112 | if the compiler used is GNU C and the version is the given version, or |
127 | compiler used is GNU C and the version is the given version, or higher. |
113 | higher. |
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114 | |
128 | |
115 | This macro tries to return false on compilers that claim to be GCC |
129 | This macro tries to return false on compilers that claim to be GCC |
116 | compatible but aren't. |
130 | compatible but aren't. |
117 | |
131 | |
118 | =item ECB_EXTERN_C |
132 | =item ECB_EXTERN_C |
… | |
… | |
137 | |
151 | |
138 | ECB_EXTERN_C_END |
152 | ECB_EXTERN_C_END |
139 | |
153 | |
140 | =item ECB_STDFP |
154 | =item ECB_STDFP |
141 | |
155 | |
142 | If this evaluates to a true value (suitable for testing in by the |
156 | If this evaluates to a true value (suitable for testing by the |
143 | preprocessor), then C<float> and C<double> use IEEE 754 single/binary32 |
157 | preprocessor), then C<float> and C<double> use IEEE 754 single/binary32 |
144 | and double/binary64 representations internally I<and> the endianness of |
158 | and double/binary64 representations internally I<and> the endianness of |
145 | both types match the endianness of C<uint32_t> and C<uint64_t>. |
159 | both types match the endianness of C<uint32_t> and C<uint64_t>. |
146 | |
160 | |
147 | This means you can just copy the bits of a C<float> (or C<double>) to an |
161 | This means you can just copy the bits of a C<float> (or C<double>) to an |
… | |
… | |
163 | C<__x86_64> stands for, well, the x86-64 ABI, making these macros |
177 | C<__x86_64> stands for, well, the x86-64 ABI, making these macros |
164 | necessary. |
178 | necessary. |
165 | |
179 | |
166 | =back |
180 | =back |
167 | |
181 | |
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182 | =head2 MACRO TRICKERY |
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183 | |
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184 | =over 4 |
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185 | |
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186 | =item ECB_CONCAT (a, b) |
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187 | |
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188 | Expands any macros in C<a> and C<b>, then concatenates the result to form |
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189 | a single token. This is mainly useful to form identifiers from components, |
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190 | e.g.: |
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191 | |
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192 | #define S1 str |
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193 | #define S2 cpy |
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194 | |
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195 | ECB_CONCAT (S1, S2)(dst, src); // == strcpy (dst, src); |
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196 | |
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197 | =item ECB_STRINGIFY (arg) |
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198 | |
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199 | Expands any macros in C<arg> and returns the stringified version of |
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200 | it. This is mainly useful to get the contents of a macro in string form, |
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201 | e.g.: |
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202 | |
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203 | #define SQL_LIMIT 100 |
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204 | sql_exec ("select * from table limit " ECB_STRINGIFY (SQL_LIMIT)); |
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205 | |
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206 | =item ECB_STRINGIFY_EXPR (expr) |
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207 | |
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208 | Like C<ECB_STRINGIFY>, but additionally evaluates C<expr> to make sure it |
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209 | is a valid expression. This is useful to catch typos or cases where the |
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210 | macro isn't available: |
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211 | |
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212 | #include <errno.h> |
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213 | |
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214 | ECB_STRINGIFY (EDOM); // "33" (on my system at least) |
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215 | ECB_STRINGIFY_EXPR (EDOM); // "33" |
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216 | |
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217 | // now imagine we had a typo: |
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218 | |
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219 | ECB_STRINGIFY (EDAM); // "EDAM" |
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220 | ECB_STRINGIFY_EXPR (EDAM); // error: EDAM undefined |
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221 | |
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222 | =back |
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223 | |
168 | =head2 GCC ATTRIBUTES |
224 | =head2 ATTRIBUTES |
169 | |
225 | |
170 | A major part of libecb deals with GCC attributes. These are additional |
226 | A major part of libecb deals with additional attributes that can be |
171 | attributes that you can assign to functions, variables and sometimes even |
227 | assigned to functions, variables and sometimes even types - much like |
172 | types - much like C<const> or C<volatile> in C. |
228 | C<const> or C<volatile> in C. They are implemented using either GCC |
173 | |
229 | attributes or other compiler/language specific features. Attributes |
174 | While GCC allows declarations to show up in many surprising places, |
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175 | but not in many expected places, the safest way is to put attribute |
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176 | declarations before the whole declaration: |
230 | declarations must be put before the whole declaration: |
177 | |
231 | |
178 | ecb_const int mysqrt (int a); |
232 | ecb_const int mysqrt (int a); |
179 | ecb_unused int i; |
233 | ecb_unused int i; |
180 | |
234 | |
181 | For variables, it is often nicer to put the attribute after the name, and |
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182 | avoid multiple declarations using commas: |
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183 | |
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184 | int i ecb_unused; |
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185 | |
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186 | =over 4 |
235 | =over 4 |
187 | |
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188 | =item ecb_attribute ((attrs...)) |
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189 | |
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190 | A simple wrapper that expands to C<__attribute__((attrs))> on GCC 3.1+ and |
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191 | Clang 2.8+, and to nothing on other compilers, so the effect is that only |
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192 | GCC and Clang see these. |
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193 | |
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194 | Example: use the C<deprecated> attribute on a function. |
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195 | |
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196 | ecb_attribute((__deprecated__)) void |
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197 | do_not_use_me_anymore (void); |
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198 | |
236 | |
199 | =item ecb_unused |
237 | =item ecb_unused |
200 | |
238 | |
201 | Marks a function or a variable as "unused", which simply suppresses a |
239 | Marks a function or a variable as "unused", which simply suppresses a |
202 | warning by GCC when it detects it as unused. This is useful when you e.g. |
240 | warning by GCC when it detects it as unused. This is useful when you e.g. |
203 | declare a variable but do not always use it: |
241 | declare a variable but do not always use it: |
204 | |
242 | |
205 | { |
243 | { |
206 | int var ecb_unused; |
244 | ecb_unused int var; |
207 | |
245 | |
208 | #ifdef SOMECONDITION |
246 | #ifdef SOMECONDITION |
209 | var = ...; |
247 | var = ...; |
210 | return var; |
248 | return var; |
211 | #else |
249 | #else |
… | |
… | |
216 | =item ecb_deprecated |
254 | =item ecb_deprecated |
217 | |
255 | |
218 | Similar to C<ecb_unused>, but marks a function, variable or type as |
256 | Similar to C<ecb_unused>, but marks a function, variable or type as |
219 | deprecated. This makes some compilers warn when the type is used. |
257 | deprecated. This makes some compilers warn when the type is used. |
220 | |
258 | |
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259 | =item ecb_deprecated_message (message) |
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260 | |
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261 | Same as C<ecb_deprecated>, but if possible, the specified diagnostic is |
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262 | used instead of a generic depreciation message when the object is being |
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263 | used. |
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264 | |
221 | =item ecb_inline |
265 | =item ecb_inline |
222 | |
266 | |
223 | This is not actually an attribute, but you use it like one. It expands |
267 | Expands either to (a compiler-specific equivalent of) C<static inline> or |
224 | either to C<static inline> or to just C<static>, if inline isn't |
268 | to just C<static>, if inline isn't supported. It should be used to declare |
225 | supported. It should be used to declare functions that should be inlined, |
269 | functions that should be inlined, for code size or speed reasons. |
226 | for code size or speed reasons. |
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227 | |
270 | |
228 | Example: inline this function, it surely will reduce codesize. |
271 | Example: inline this function, it surely will reduce codesize. |
229 | |
272 | |
230 | ecb_inline int |
273 | ecb_inline int |
231 | negmul (int a, int b) |
274 | negmul (int a, int b) |
… | |
… | |
233 | return - (a * b); |
276 | return - (a * b); |
234 | } |
277 | } |
235 | |
278 | |
236 | =item ecb_noinline |
279 | =item ecb_noinline |
237 | |
280 | |
238 | Prevent a function from being inlined - it might be optimised away, but |
281 | Prevents a function from being inlined - it might be optimised away, but |
239 | not inlined into other functions. This is useful if you know your function |
282 | not inlined into other functions. This is useful if you know your function |
240 | is rarely called and large enough for inlining not to be helpful. |
283 | is rarely called and large enough for inlining not to be helpful. |
241 | |
284 | |
242 | =item ecb_noreturn |
285 | =item ecb_noreturn |
243 | |
286 | |
… | |
… | |
264 | |
307 | |
265 | Example: multiply a vector, and allow the compiler to parallelise the |
308 | Example: multiply a vector, and allow the compiler to parallelise the |
266 | loop, because it knows it doesn't overwrite input values. |
309 | loop, because it knows it doesn't overwrite input values. |
267 | |
310 | |
268 | void |
311 | void |
269 | multiply (float *ecb_restrict src, |
312 | multiply (ecb_restrict float *src, |
270 | float *ecb_restrict dst, |
313 | ecb_restrict float *dst, |
271 | int len, float factor) |
314 | int len, float factor) |
272 | { |
315 | { |
273 | int i; |
316 | int i; |
274 | |
317 | |
275 | for (i = 0; i < len; ++i) |
318 | for (i = 0; i < len; ++i) |
… | |
… | |
401 | return is_constant (n) && !(n & (n - 1)) |
444 | return is_constant (n) && !(n & (n - 1)) |
402 | ? rndm16 () & (num - 1) |
445 | ? rndm16 () & (num - 1) |
403 | : (n * (uint32_t)rndm16 ()) >> 16; |
446 | : (n * (uint32_t)rndm16 ()) >> 16; |
404 | } |
447 | } |
405 | |
448 | |
406 | =item bool ecb_expect (expr, value) |
449 | =item ecb_expect (expr, value) |
407 | |
450 | |
408 | Evaluates C<expr> and returns it. In addition, it tells the compiler that |
451 | Evaluates C<expr> and returns it. In addition, it tells the compiler that |
409 | the C<expr> evaluates to C<value> a lot, which can be used for static |
452 | the C<expr> evaluates to C<value> a lot, which can be used for static |
410 | branch optimisations. |
453 | branch optimisations. |
411 | |
454 | |
… | |
… | |
458 | { |
501 | { |
459 | if (ecb_expect_false (current + size > end)) |
502 | if (ecb_expect_false (current + size > end)) |
460 | real_reserve_method (size); /* presumably noinline */ |
503 | real_reserve_method (size); /* presumably noinline */ |
461 | } |
504 | } |
462 | |
505 | |
463 | =item bool ecb_assume (cond) |
506 | =item ecb_assume (cond) |
464 | |
507 | |
465 | Try to tell the compiler that some condition is true, even if it's not |
508 | Tries to tell the compiler that some condition is true, even if it's not |
466 | obvious. |
509 | obvious. This is not a function, but a statement: it cannot be used in |
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510 | another expression. |
467 | |
511 | |
468 | This can be used to teach the compiler about invariants or other |
512 | This can be used to teach the compiler about invariants or other |
469 | conditions that might improve code generation, but which are impossible to |
513 | conditions that might improve code generation, but which are impossible to |
470 | deduce form the code itself. |
514 | deduce form the code itself. |
471 | |
515 | |
… | |
… | |
488 | |
532 | |
489 | Then the compiler I<might> be able to optimise out the second call |
533 | Then the compiler I<might> be able to optimise out the second call |
490 | completely, as it knows that C<< current + 1 > end >> is false and the |
534 | completely, as it knows that C<< current + 1 > end >> is false and the |
491 | call will never be executed. |
535 | call will never be executed. |
492 | |
536 | |
493 | =item bool ecb_unreachable () |
537 | =item ecb_unreachable () |
494 | |
538 | |
495 | This function does nothing itself, except tell the compiler that it will |
539 | This function does nothing itself, except tell the compiler that it will |
496 | never be executed. Apart from suppressing a warning in some cases, this |
540 | never be executed. Apart from suppressing a warning in some cases, this |
497 | function can be used to implement C<ecb_assume> or similar functions. |
541 | function can be used to implement C<ecb_assume> or similar functionality. |
498 | |
542 | |
499 | =item bool ecb_prefetch (addr, rw, locality) |
543 | =item ecb_prefetch (addr, rw, locality) |
500 | |
544 | |
501 | Tells the compiler to try to prefetch memory at the given C<addr>ess |
545 | Tells the compiler to try to prefetch memory at the given C<addr>ess |
502 | for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of |
546 | for either reading (C<rw> = 0) or writing (C<rw> = 1). A C<locality> of |
503 | C<0> means that there will only be one access later, C<3> means that |
547 | C<0> means that there will only be one access later, C<3> means that |
504 | the data will likely be accessed very often, and values in between mean |
548 | the data will likely be accessed very often, and values in between mean |
505 | something... in between. The memory pointed to by the address does not |
549 | something... in between. The memory pointed to by the address does not |
506 | need to be accessible (it could be a null pointer for example), but C<rw> |
550 | need to be accessible (it could be a null pointer for example), but C<rw> |
507 | and C<locality> must be compile-time constants. |
551 | and C<locality> must be compile-time constants. |
508 | |
552 | |
|
|
553 | This is a statement, not a function: you cannot use it as part of an |
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|
554 | expression. |
|
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555 | |
509 | An obvious way to use this is to prefetch some data far away, in a big |
556 | An obvious way to use this is to prefetch some data far away, in a big |
510 | array you loop over. This prefetches memory some 128 array elements later, |
557 | array you loop over. This prefetches memory some 128 array elements later, |
511 | in the hope that it will be ready when the CPU arrives at that location. |
558 | in the hope that it will be ready when the CPU arrives at that location. |
512 | |
559 | |
513 | int sum = 0; |
560 | int sum = 0; |
… | |
… | |
550 | |
597 | |
551 | =item int ecb_ctz32 (uint32_t x) |
598 | =item int ecb_ctz32 (uint32_t x) |
552 | |
599 | |
553 | =item int ecb_ctz64 (uint64_t x) |
600 | =item int ecb_ctz64 (uint64_t x) |
554 | |
601 | |
|
|
602 | =item int ecb_ctz (T x) [C++] |
|
|
603 | |
555 | Returns the index of the least significant bit set in C<x> (or |
604 | Returns the index of the least significant bit set in C<x> (or |
556 | equivalently the number of bits set to 0 before the least significant bit |
605 | equivalently the number of bits set to 0 before the least significant bit |
557 | set), starting from 0. If C<x> is 0 the result is undefined. |
606 | set), starting from 0. If C<x> is 0 the result is undefined. |
558 | |
607 | |
559 | For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>. |
608 | For smaller types than C<uint32_t> you can safely use C<ecb_ctz32>. |
560 | |
609 | |
|
|
610 | The overloaded C++ C<ecb_ctz> function supports C<uint8_t>, C<uint16_t>, |
|
|
611 | C<uint32_t> and C<uint64_t> types. |
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612 | |
561 | For example: |
613 | For example: |
562 | |
614 | |
563 | ecb_ctz32 (3) = 0 |
615 | ecb_ctz32 (3) = 0 |
564 | ecb_ctz32 (6) = 1 |
616 | ecb_ctz32 (6) = 1 |
565 | |
617 | |
566 | =item bool ecb_is_pot32 (uint32_t x) |
618 | =item bool ecb_is_pot32 (uint32_t x) |
567 | |
619 | |
568 | =item bool ecb_is_pot64 (uint32_t x) |
620 | =item bool ecb_is_pot64 (uint32_t x) |
569 | |
621 | |
|
|
622 | =item bool ecb_is_pot (T x) [C++] |
|
|
623 | |
570 | Return true iff C<x> is a power of two or C<x == 0>. |
624 | Returns true iff C<x> is a power of two or C<x == 0>. |
571 | |
625 | |
572 | For smaller types then C<uint32_t> you can safely use C<ecb_is_pot32>. |
626 | For smaller types than C<uint32_t> you can safely use C<ecb_is_pot32>. |
|
|
627 | |
|
|
628 | The overloaded C++ C<ecb_is_pot> function supports C<uint8_t>, C<uint16_t>, |
|
|
629 | C<uint32_t> and C<uint64_t> types. |
573 | |
630 | |
574 | =item int ecb_ld32 (uint32_t x) |
631 | =item int ecb_ld32 (uint32_t x) |
575 | |
632 | |
576 | =item int ecb_ld64 (uint64_t x) |
633 | =item int ecb_ld64 (uint64_t x) |
|
|
634 | |
|
|
635 | =item int ecb_ld64 (T x) [C++] |
577 | |
636 | |
578 | Returns the index of the most significant bit set in C<x>, or the number |
637 | Returns the index of the most significant bit set in C<x>, or the number |
579 | of digits the number requires in binary (so that C<< 2**ld <= x < |
638 | of digits the number requires in binary (so that C<< 2**ld <= x < |
580 | 2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is |
639 | 2**(ld+1) >>). If C<x> is 0 the result is undefined. A common use case is |
581 | to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for |
640 | to compute the integer binary logarithm, i.e. C<floor (log2 (n))>, for |
… | |
… | |
586 | the given data type), while C<ecb_ld> returns how many bits the number |
645 | the given data type), while C<ecb_ld> returns how many bits the number |
587 | itself requires. |
646 | itself requires. |
588 | |
647 | |
589 | For smaller types than C<uint32_t> you can safely use C<ecb_ld32>. |
648 | For smaller types than C<uint32_t> you can safely use C<ecb_ld32>. |
590 | |
649 | |
|
|
650 | The overloaded C++ C<ecb_ld> function supports C<uint8_t>, C<uint16_t>, |
|
|
651 | C<uint32_t> and C<uint64_t> types. |
|
|
652 | |
591 | =item int ecb_popcount32 (uint32_t x) |
653 | =item int ecb_popcount32 (uint32_t x) |
592 | |
654 | |
593 | =item int ecb_popcount64 (uint64_t x) |
655 | =item int ecb_popcount64 (uint64_t x) |
594 | |
656 | |
|
|
657 | =item int ecb_popcount (T x) [C++] |
|
|
658 | |
595 | Returns the number of bits set to 1 in C<x>. |
659 | Returns the number of bits set to 1 in C<x>. |
596 | |
660 | |
597 | For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>. |
661 | For smaller types than C<uint32_t> you can safely use C<ecb_popcount32>. |
|
|
662 | |
|
|
663 | The overloaded C++ C<ecb_popcount> function supports C<uint8_t>, C<uint16_t>, |
|
|
664 | C<uint32_t> and C<uint64_t> types. |
598 | |
665 | |
599 | For example: |
666 | For example: |
600 | |
667 | |
601 | ecb_popcount32 (7) = 3 |
668 | ecb_popcount32 (7) = 3 |
602 | ecb_popcount32 (255) = 8 |
669 | ecb_popcount32 (255) = 8 |
… | |
… | |
605 | |
672 | |
606 | =item uint16_t ecb_bitrev16 (uint16_t x) |
673 | =item uint16_t ecb_bitrev16 (uint16_t x) |
607 | |
674 | |
608 | =item uint32_t ecb_bitrev32 (uint32_t x) |
675 | =item uint32_t ecb_bitrev32 (uint32_t x) |
609 | |
676 | |
|
|
677 | =item T ecb_bitrev (T x) [C++] |
|
|
678 | |
610 | Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1 |
679 | Reverses the bits in x, i.e. the MSB becomes the LSB, MSB-1 becomes LSB+1 |
611 | and so on. |
680 | and so on. |
612 | |
681 | |
|
|
682 | The overloaded C++ C<ecb_bitrev> function supports C<uint8_t>, C<uint16_t> and C<uint32_t> types. |
|
|
683 | |
613 | Example: |
684 | Example: |
614 | |
685 | |
615 | ecb_bitrev8 (0xa7) = 0xea |
686 | ecb_bitrev8 (0xa7) = 0xea |
616 | ecb_bitrev32 (0xffcc4411) = 0x882233ff |
687 | ecb_bitrev32 (0xffcc4411) = 0x882233ff |
617 | |
688 | |
|
|
689 | =item T ecb_bitrev (T x) [C++] |
|
|
690 | |
|
|
691 | Overloaded C++ bitrev function. |
|
|
692 | |
|
|
693 | C<T> must be one of C<uint8_t>, C<uint16_t> or C<uint32_t>. |
|
|
694 | |
618 | =item uint32_t ecb_bswap16 (uint32_t x) |
695 | =item uint32_t ecb_bswap16 (uint32_t x) |
619 | |
696 | |
620 | =item uint32_t ecb_bswap32 (uint32_t x) |
697 | =item uint32_t ecb_bswap32 (uint32_t x) |
621 | |
698 | |
622 | =item uint64_t ecb_bswap64 (uint64_t x) |
699 | =item uint64_t ecb_bswap64 (uint64_t x) |
|
|
700 | |
|
|
701 | =item T ecb_bswap (T x) |
623 | |
702 | |
624 | These functions return the value of the 16-bit (32-bit, 64-bit) value |
703 | These functions return the value of the 16-bit (32-bit, 64-bit) value |
625 | C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in |
704 | C<x> after reversing the order of bytes (0x11223344 becomes 0x44332211 in |
626 | C<ecb_bswap32>). |
705 | C<ecb_bswap32>). |
627 | |
706 | |
|
|
707 | The overloaded C++ C<ecb_bswap> function supports C<uint8_t>, C<uint16_t>, |
|
|
708 | C<uint32_t> and C<uint64_t> types. |
|
|
709 | |
628 | =item uint8_t ecb_rotl8 (uint8_t x, unsigned int count) |
710 | =item uint8_t ecb_rotl8 (uint8_t x, unsigned int count) |
629 | |
711 | |
630 | =item uint16_t ecb_rotl16 (uint16_t x, unsigned int count) |
712 | =item uint16_t ecb_rotl16 (uint16_t x, unsigned int count) |
631 | |
713 | |
632 | =item uint32_t ecb_rotl32 (uint32_t x, unsigned int count) |
714 | =item uint32_t ecb_rotl32 (uint32_t x, unsigned int count) |
… | |
… | |
647 | |
729 | |
648 | Current GCC versions understand these functions and usually compile them |
730 | Current GCC versions understand these functions and usually compile them |
649 | to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on |
731 | to "optimal" code (e.g. a single C<rol> or a combination of C<shld> on |
650 | x86). |
732 | x86). |
651 | |
733 | |
|
|
734 | =item T ecb_rotl (T x, unsigned int count) [C++] |
|
|
735 | |
|
|
736 | =item T ecb_rotr (T x, unsigned int count) [C++] |
|
|
737 | |
|
|
738 | Overloaded C++ rotl/rotr functions. |
|
|
739 | |
|
|
740 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
|
|
741 | |
652 | =back |
742 | =back |
653 | |
743 | |
|
|
744 | =head2 HOST ENDIANNESS CONVERSION |
|
|
745 | |
|
|
746 | =over 4 |
|
|
747 | |
|
|
748 | =item uint_fast16_t ecb_be_u16_to_host (uint_fast16_t v) |
|
|
749 | |
|
|
750 | =item uint_fast32_t ecb_be_u32_to_host (uint_fast32_t v) |
|
|
751 | |
|
|
752 | =item uint_fast64_t ecb_be_u64_to_host (uint_fast64_t v) |
|
|
753 | |
|
|
754 | =item uint_fast16_t ecb_le_u16_to_host (uint_fast16_t v) |
|
|
755 | |
|
|
756 | =item uint_fast32_t ecb_le_u32_to_host (uint_fast32_t v) |
|
|
757 | |
|
|
758 | =item uint_fast64_t ecb_le_u64_to_host (uint_fast64_t v) |
|
|
759 | |
|
|
760 | Convert an unsigned 16, 32 or 64 bit value from big or little endian to host byte order. |
|
|
761 | |
|
|
762 | The naming convention is C<ecb_>(C<be>|C<le>)C<_u>C<16|32|64>C<_to_host>, |
|
|
763 | where C<be> and C<le> stand for big endian and little endian, respectively. |
|
|
764 | |
|
|
765 | =item uint_fast16_t ecb_host_to_be_u16 (uint_fast16_t v) |
|
|
766 | |
|
|
767 | =item uint_fast32_t ecb_host_to_be_u32 (uint_fast32_t v) |
|
|
768 | |
|
|
769 | =item uint_fast64_t ecb_host_to_be_u64 (uint_fast64_t v) |
|
|
770 | |
|
|
771 | =item uint_fast16_t ecb_host_to_le_u16 (uint_fast16_t v) |
|
|
772 | |
|
|
773 | =item uint_fast32_t ecb_host_to_le_u32 (uint_fast32_t v) |
|
|
774 | |
|
|
775 | =item uint_fast64_t ecb_host_to_le_u64 (uint_fast64_t v) |
|
|
776 | |
|
|
777 | Like above, but converts I<from> host byte order to the specified |
|
|
778 | endianness. |
|
|
779 | |
|
|
780 | =back |
|
|
781 | |
|
|
782 | In C++ the following additional template functions are supported: |
|
|
783 | |
|
|
784 | =over 4 |
|
|
785 | |
|
|
786 | =item T ecb_be_to_host (T v) |
|
|
787 | |
|
|
788 | =item T ecb_le_to_host (T v) |
|
|
789 | |
|
|
790 | =item T ecb_host_to_be (T v) |
|
|
791 | |
|
|
792 | =item T ecb_host_to_le (T v) |
|
|
793 | |
|
|
794 | These functions work like their C counterparts, above, but use templates, |
|
|
795 | which make them useful in generic code. |
|
|
796 | |
|
|
797 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t> |
|
|
798 | (so unlike their C counterparts, there is a version for C<uint8_t>, which |
|
|
799 | again can be useful in generic code). |
|
|
800 | |
|
|
801 | =head2 UNALIGNED LOAD/STORE |
|
|
802 | |
|
|
803 | These function load or store unaligned multi-byte values. |
|
|
804 | |
|
|
805 | =over 4 |
|
|
806 | |
|
|
807 | =item uint_fast16_t ecb_peek_u16_u (const void *ptr) |
|
|
808 | |
|
|
809 | =item uint_fast32_t ecb_peek_u32_u (const void *ptr) |
|
|
810 | |
|
|
811 | =item uint_fast64_t ecb_peek_u64_u (const void *ptr) |
|
|
812 | |
|
|
813 | These functions load an unaligned, unsigned 16, 32 or 64 bit value from |
|
|
814 | memory. |
|
|
815 | |
|
|
816 | =item uint_fast16_t ecb_peek_be_u16_u (const void *ptr) |
|
|
817 | |
|
|
818 | =item uint_fast32_t ecb_peek_be_u32_u (const void *ptr) |
|
|
819 | |
|
|
820 | =item uint_fast64_t ecb_peek_be_u64_u (const void *ptr) |
|
|
821 | |
|
|
822 | =item uint_fast16_t ecb_peek_le_u16_u (const void *ptr) |
|
|
823 | |
|
|
824 | =item uint_fast32_t ecb_peek_le_u32_u (const void *ptr) |
|
|
825 | |
|
|
826 | =item uint_fast64_t ecb_peek_le_u64_u (const void *ptr) |
|
|
827 | |
|
|
828 | Like above, but additionally convert from big endian (C<be>) or little |
|
|
829 | endian (C<le>) byte order to host byte order while doing so. |
|
|
830 | |
|
|
831 | =item ecb_poke_u16_u (void *ptr, uint16_t v) |
|
|
832 | |
|
|
833 | =item ecb_poke_u32_u (void *ptr, uint32_t v) |
|
|
834 | |
|
|
835 | =item ecb_poke_u64_u (void *ptr, uint64_t v) |
|
|
836 | |
|
|
837 | These functions store an unaligned, unsigned 16, 32 or 64 bit value to |
|
|
838 | memory. |
|
|
839 | |
|
|
840 | =item ecb_poke_be_u16_u (void *ptr, uint_fast16_t v) |
|
|
841 | |
|
|
842 | =item ecb_poke_be_u32_u (void *ptr, uint_fast32_t v) |
|
|
843 | |
|
|
844 | =item ecb_poke_be_u64_u (void *ptr, uint_fast64_t v) |
|
|
845 | |
|
|
846 | =item ecb_poke_le_u16_u (void *ptr, uint_fast16_t v) |
|
|
847 | |
|
|
848 | =item ecb_poke_le_u32_u (void *ptr, uint_fast32_t v) |
|
|
849 | |
|
|
850 | =item ecb_poke_le_u64_u (void *ptr, uint_fast64_t v) |
|
|
851 | |
|
|
852 | Like above, but additionally convert from host byte order to big endian |
|
|
853 | (C<be>) or little endian (C<le>) byte order while doing so. |
|
|
854 | |
|
|
855 | =back |
|
|
856 | |
|
|
857 | In C++ the following additional template functions are supported: |
|
|
858 | |
|
|
859 | =over 4 |
|
|
860 | |
|
|
861 | =item T ecb_peek<T> (const void *ptr) |
|
|
862 | |
|
|
863 | =item T ecb_peek_be<T> (const void *ptr) |
|
|
864 | |
|
|
865 | =item T ecb_peek_le<T> (const void *ptr) |
|
|
866 | |
|
|
867 | =item T ecb_peek_u<T> (const void *ptr) |
|
|
868 | |
|
|
869 | =item T ecb_peek_be_u<T> (const void *ptr) |
|
|
870 | |
|
|
871 | =item T ecb_peek_le_u<T> (const void *ptr) |
|
|
872 | |
|
|
873 | Similarly to their C counterparts, these functions load an unsigned 8, 16, |
|
|
874 | 32 or 64 bit value from memory, with optional conversion from big/little |
|
|
875 | endian. |
|
|
876 | |
|
|
877 | Since the type cannot be deduced, it has to be specified explicitly, e.g. |
|
|
878 | |
|
|
879 | uint_fast16_t v = ecb_peek<uint16_t> (ptr); |
|
|
880 | |
|
|
881 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
|
|
882 | |
|
|
883 | Unlike their C counterparts, these functions support 8 bit quantities |
|
|
884 | (C<uint8_t>) and also have an aligned version (without the C<_u> prefix), |
|
|
885 | all of which hopefully makes them more useful in generic code. |
|
|
886 | |
|
|
887 | =item ecb_poke (void *ptr, T v) |
|
|
888 | |
|
|
889 | =item ecb_poke_be (void *ptr, T v) |
|
|
890 | |
|
|
891 | =item ecb_poke_le (void *ptr, T v) |
|
|
892 | |
|
|
893 | =item ecb_poke_u (void *ptr, T v) |
|
|
894 | |
|
|
895 | =item ecb_poke_be_u (void *ptr, T v) |
|
|
896 | |
|
|
897 | =item ecb_poke_le_u (void *ptr, T v) |
|
|
898 | |
|
|
899 | Again, similarly to their C counterparts, these functions store an |
|
|
900 | unsigned 8, 16, 32 or z64 bit value to memory, with optional conversion to |
|
|
901 | big/little endian. |
|
|
902 | |
|
|
903 | C<T> must be one of C<uint8_t>, C<uint16_t>, C<uint32_t> or C<uint64_t>. |
|
|
904 | |
|
|
905 | Unlike their C counterparts, these functions support 8 bit quantities |
|
|
906 | (C<uint8_t>) and also have an aligned version (without the C<_u> prefix), |
|
|
907 | all of which hopefully makes them more useful in generic code. |
|
|
908 | |
|
|
909 | =back |
|
|
910 | |
654 | =head2 FLOATING POINT FIDDLING |
911 | =head2 FLOATING POINT FIDDLING |
655 | |
912 | |
656 | =over 4 |
913 | =over 4 |
657 | |
914 | |
|
|
915 | =item ECB_INFINITY [-UECB_NO_LIBM] |
|
|
916 | |
|
|
917 | Evaluates to positive infinity if supported by the platform, otherwise to |
|
|
918 | a truly huge number. |
|
|
919 | |
|
|
920 | =item ECB_NAN [-UECB_NO_LIBM] |
|
|
921 | |
|
|
922 | Evaluates to a quiet NAN if supported by the platform, otherwise to |
|
|
923 | C<ECB_INFINITY>. |
|
|
924 | |
|
|
925 | =item float ecb_ldexpf (float x, int exp) [-UECB_NO_LIBM] |
|
|
926 | |
|
|
927 | Same as C<ldexpf>, but always available. |
|
|
928 | |
|
|
929 | =item uint32_t ecb_float_to_binary16 (float x) [-UECB_NO_LIBM] |
|
|
930 | |
658 | =item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM] |
931 | =item uint32_t ecb_float_to_binary32 (float x) [-UECB_NO_LIBM] |
659 | |
932 | |
660 | =item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM] |
933 | =item uint64_t ecb_double_to_binary64 (double x) [-UECB_NO_LIBM] |
661 | |
934 | |
662 | These functions each take an argument in the native C<float> or C<double> |
935 | These functions each take an argument in the native C<float> or C<double> |
663 | type and return the IEEE 754 bit representation of it. |
936 | type and return the IEEE 754 bit representation of it (binary16/half, |
|
|
937 | binary32/single or binary64/double precision). |
664 | |
938 | |
665 | The bit representation is just as IEEE 754 defines it, i.e. the sign bit |
939 | The bit representation is just as IEEE 754 defines it, i.e. the sign bit |
666 | will be the most significant bit, followed by exponent and mantissa. |
940 | will be the most significant bit, followed by exponent and mantissa. |
667 | |
941 | |
668 | This function should work even when the native floating point format isn't |
942 | This function should work even when the native floating point format isn't |
… | |
… | |
672 | |
946 | |
673 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
947 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
674 | be able to optimise away this function completely. |
948 | be able to optimise away this function completely. |
675 | |
949 | |
676 | These functions can be helpful when serialising floats to the network - you |
950 | These functions can be helpful when serialising floats to the network - you |
677 | can serialise the return value like a normal uint32_t/uint64_t. |
951 | can serialise the return value like a normal uint16_t/uint32_t/uint64_t. |
678 | |
952 | |
679 | Another use for these functions is to manipulate floating point values |
953 | Another use for these functions is to manipulate floating point values |
680 | directly. |
954 | directly. |
681 | |
955 | |
682 | Silly example: toggle the sign bit of a float. |
956 | Silly example: toggle the sign bit of a float. |
… | |
… | |
689 | |
963 | |
690 | =item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM] |
964 | =item float ecb_binary16_to_float (uint16_t x) [-UECB_NO_LIBM] |
691 | |
965 | |
692 | =item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM] |
966 | =item float ecb_binary32_to_float (uint32_t x) [-UECB_NO_LIBM] |
693 | |
967 | |
694 | =item double ecb_binary32_to_double (uint64_t x) [-UECB_NO_LIBM] |
968 | =item double ecb_binary64_to_double (uint64_t x) [-UECB_NO_LIBM] |
695 | |
969 | |
696 | The reverse operation of the previous function - takes the bit |
970 | The reverse operation of the previous function - takes the bit |
697 | representation of an IEEE binary16, binary32 or binary64 number and |
971 | representation of an IEEE binary16, binary32 or binary64 number (half, |
698 | converts it to the native C<float> or C<double> format. |
972 | single or double precision) and converts it to the native C<float> or |
|
|
973 | C<double> format. |
699 | |
974 | |
700 | This function should work even when the native floating point format isn't |
975 | This function should work even when the native floating point format isn't |
701 | IEEE compliant, of course at a speed and code size penalty, and of course |
976 | IEEE compliant, of course at a speed and code size penalty, and of course |
702 | also within reasonable limits (it tries to convert normals and denormals, |
977 | also within reasonable limits (it tries to convert normals and denormals, |
703 | and might be lucky for infinities, and with extraordinary luck, also for |
978 | and might be lucky for infinities, and with extraordinary luck, also for |
704 | negative zero). |
979 | negative zero). |
705 | |
980 | |
706 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
981 | On all modern platforms (where C<ECB_STDFP> is true), the compiler should |
707 | be able to optimise away this function completely. |
982 | be able to optimise away this function completely. |
|
|
983 | |
|
|
984 | =item uint16_t ecb_binary32_to_binary16 (uint32_t x) |
|
|
985 | |
|
|
986 | =item uint32_t ecb_binary16_to_binary32 (uint16_t x) |
|
|
987 | |
|
|
988 | Convert a IEEE binary32/single precision to binary16/half format, and vice |
|
|
989 | versa, handling all details (round-to-nearest-even, subnormals, infinity |
|
|
990 | and NaNs) correctly. |
|
|
991 | |
|
|
992 | These are functions are available under C<-DECB_NO_LIBM>, since |
|
|
993 | they do not rely on the platform floating point format. The |
|
|
994 | C<ecb_float_to_binary16> and C<ecb_binary16_to_float> functions are |
|
|
995 | usually what you want. |
708 | |
996 | |
709 | =back |
997 | =back |
710 | |
998 | |
711 | =head2 ARITHMETIC |
999 | =head2 ARITHMETIC |
712 | |
1000 | |
… | |
… | |
793 | dependencies on the math library (usually called F<-lm>) - these are |
1081 | dependencies on the math library (usually called F<-lm>) - these are |
794 | marked with [-UECB_NO_LIBM]. |
1082 | marked with [-UECB_NO_LIBM]. |
795 | |
1083 | |
796 | =back |
1084 | =back |
797 | |
1085 | |
|
|
1086 | =head1 UNDOCUMENTED FUNCTIONALITY |
798 | |
1087 | |
|
|
1088 | F<ecb.h> is full of undocumented functionality as well, some of which is |
|
|
1089 | intended to be internal-use only, some of which we forgot to document, and |
|
|
1090 | some of which we hide because we are not sure we will keep the interface |
|
|
1091 | stable. |
|
|
1092 | |
|
|
1093 | While you are welcome to rummage around and use whatever you find useful |
|
|
1094 | (we can't stop you), keep in mind that we will change undocumented |
|
|
1095 | functionality in incompatible ways without thinking twice, while we are |
|
|
1096 | considerably more conservative with documented things. |
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1098 | =head1 AUTHORS |
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1099 | |
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1100 | C<libecb> is designed and maintained by: |
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1101 | |
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1102 | Emanuele Giaquinta <e.giaquinta@glauco.it> |
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1103 | Marc Alexander Lehmann <schmorp@schmorp.de> |
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1105 | |