… | |
… | |
11 | The newest version of this document is also available as an html-formatted |
11 | The newest version of this document is also available as an html-formatted |
12 | web page you might find easier to navigate when reading it for the first |
12 | web page you might find easier to navigate when reading it for the first |
13 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libeio/eio.pod>. |
13 | time: L<http://pod.tst.eu/http://cvs.schmorp.de/libeio/eio.pod>. |
14 | |
14 | |
15 | Note that this library is a by-product of the C<IO::AIO> perl |
15 | Note that this library is a by-product of the C<IO::AIO> perl |
16 | module, and many of the subtler points regarding requets lifetime |
16 | module, and many of the subtler points regarding requests lifetime |
17 | and so on are only documented in its documentation at the |
17 | and so on are only documented in its documentation at the |
18 | moment: L<http://pod.tst.eu/http://cvs.schmorp.de/IO-AIO/AIO.pm>. |
18 | moment: L<http://pod.tst.eu/http://cvs.schmorp.de/IO-AIO/AIO.pm>. |
19 | |
19 | |
20 | =head2 FEATURES |
20 | =head2 FEATURES |
21 | |
21 | |
22 | This library provides fully asynchronous versions of most POSIX functions |
22 | This library provides fully asynchronous versions of most POSIX functions |
23 | dealign with I/O. Unlike most asynchronous libraries, this not only |
23 | dealing with I/O. Unlike most asynchronous libraries, this not only |
24 | includes C<read> and C<write>, but also C<open>, C<stat>, C<unlink> and |
24 | includes C<read> and C<write>, but also C<open>, C<stat>, C<unlink> and |
25 | similar functions, as well as less rarely ones such as C<mknod>, C<futime> |
25 | similar functions, as well as less rarely ones such as C<mknod>, C<futime> |
26 | or C<readlink>. |
26 | or C<readlink>. |
27 | |
27 | |
28 | It also offers wrappers around C<sendfile> (Solaris, Linux, HP-UX and |
28 | It also offers wrappers around C<sendfile> (Solaris, Linux, HP-UX and |
… | |
… | |
37 | =head2 TIME REPRESENTATION |
37 | =head2 TIME REPRESENTATION |
38 | |
38 | |
39 | Libeio represents time as a single floating point number, representing the |
39 | Libeio represents time as a single floating point number, representing the |
40 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
40 | (fractional) number of seconds since the (POSIX) epoch (somewhere near |
41 | the beginning of 1970, details are complicated, don't ask). This type is |
41 | the beginning of 1970, details are complicated, don't ask). This type is |
42 | called C<eio_tstamp>, but it is guarenteed to be of type C<double> (or |
42 | called C<eio_tstamp>, but it is guaranteed to be of type C<double> (or |
43 | better), so you can freely use C<double> yourself. |
43 | better), so you can freely use C<double> yourself. |
44 | |
44 | |
45 | Unlike the name component C<stamp> might indicate, it is also used for |
45 | Unlike the name component C<stamp> might indicate, it is also used for |
46 | time differences throughout libeio. |
46 | time differences throughout libeio. |
47 | |
47 | |
… | |
… | |
55 | 3. in the parent, continue business as usual, done |
55 | 3. in the parent, continue business as usual, done |
56 | 4. in the child, destroy all ready and pending requests and free the |
56 | 4. in the child, destroy all ready and pending requests and free the |
57 | memory used by the worker threads. This gives you a fully empty |
57 | memory used by the worker threads. This gives you a fully empty |
58 | libeio queue. |
58 | libeio queue. |
59 | |
59 | |
|
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60 | Note, however, since libeio does use threads, thr above guarantee doesn't |
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61 | cover your libc, for example, malloc and other libc functions are not |
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62 | fork-safe, so there is very little you can do after a fork, and in fatc, |
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63 | the above might crash, and thus change. |
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64 | |
60 | =head1 INITIALISATION/INTEGRATION |
65 | =head1 INITIALISATION/INTEGRATION |
61 | |
66 | |
62 | Before you can call any eio functions you first have to initialise the |
67 | Before you can call any eio functions you first have to initialise the |
63 | library. The library integrates into any event loop, but can also be used |
68 | library. The library integrates into any event loop, but can also be used |
64 | without one, including in polling mode. |
69 | without one, including in polling mode. |
… | |
… | |
97 | handled or C<done_poll> has been called, which signals the same. |
102 | handled or C<done_poll> has been called, which signals the same. |
98 | |
103 | |
99 | Note that C<eio_poll> might return after C<done_poll> and C<want_poll> |
104 | Note that C<eio_poll> might return after C<done_poll> and C<want_poll> |
100 | have been called again, so watch out for races in your code. |
105 | have been called again, so watch out for races in your code. |
101 | |
106 | |
102 | As with C<want_poll>, this callback is called while lcoks are being held, |
107 | As with C<want_poll>, this callback is called while locks are being held, |
103 | so you I<must not call any libeio functions form within this callback>. |
108 | so you I<must not call any libeio functions form within this callback>. |
104 | |
109 | |
105 | =item int eio_poll () |
110 | =item int eio_poll () |
106 | |
111 | |
107 | This function has to be called whenever there are pending requests that |
112 | This function has to be called whenever there are pending requests that |
… | |
… | |
126 | libev resets/rearms the async watcher before calling your callback, |
131 | libev resets/rearms the async watcher before calling your callback, |
127 | and therefore, before calling C<eio_poll>. This might result in (some) |
132 | and therefore, before calling C<eio_poll>. This might result in (some) |
128 | spurious wake-ups, but is generally harmless. |
133 | spurious wake-ups, but is generally harmless. |
129 | |
134 | |
130 | For most other event loops, you would typically use a pipe - the event |
135 | For most other event loops, you would typically use a pipe - the event |
131 | loop should be told to wait for read readyness on the read end. In |
136 | loop should be told to wait for read readiness on the read end. In |
132 | C<want_poll> you would write a single byte, in C<done_poll> you would try |
137 | C<want_poll> you would write a single byte, in C<done_poll> you would try |
133 | to read that byte, and in the callback for the read end, you would call |
138 | to read that byte, and in the callback for the read end, you would call |
134 | C<eio_poll>. The race is avoided here because the event loop should invoke |
139 | C<eio_poll>. The race is avoided here because the event loop should invoke |
135 | your callback again and again until the byte has been read (as the pipe |
140 | your callback again and again until the byte has been read (as the pipe |
136 | read callback does not read it, only C<done_poll>). |
141 | read callback does not read it, only C<done_poll>). |
137 | |
142 | |
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143 | |
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144 | =head1 HIGH LEVEL REQUEST API |
|
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145 | |
|
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146 | Libeio has both a high-level API, which consists of calling a request |
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147 | function with a callback to be called on completion, and a low-level API |
|
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148 | where you fill out request structures and submit them. |
|
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149 | |
|
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150 | This section describes the high-level API. |
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151 | |
|
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152 | =head2 REQUEST SUBMISSION AND RESULT PROCESSING |
|
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153 | |
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154 | You submit a request by calling the relevant C<eio_TYPE> function with the |
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155 | required parameters, a callback of type C<int (*eio_cb)(eio_req *req)> |
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156 | (called C<eio_cb> below) and a freely usable C<void *data> argument. |
|
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157 | |
|
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158 | The return value will either be 0 |
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159 | |
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160 | The callback will be called with an C<eio_req *> which contains the |
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161 | results of the request. The members you can access inside that structure |
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162 | vary from request to request, except for: |
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163 | |
|
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164 | =over 4 |
|
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165 | |
|
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166 | =item C<ssize_t result> |
|
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167 | |
|
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168 | This contains the result value from the call (usually the same as the |
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169 | syscall of the same name). |
|
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170 | |
|
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171 | =item C<int errorno> |
|
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172 | |
|
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173 | This contains the value of C<errno> after the call. |
|
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174 | |
|
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175 | =item C<void *data> |
|
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176 | |
|
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177 | The C<void *data> member simply stores the value of the C<data> argument. |
|
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178 | |
|
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179 | =back |
|
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180 | |
|
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181 | The return value of the callback is normally C<0>, which tells libeio to |
|
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182 | continue normally. If a callback returns a nonzero value, libeio will |
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183 | stop processing results (in C<eio_poll>) and will return the value to its |
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184 | caller. |
|
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185 | |
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186 | Memory areas passed to libeio must stay valid as long as a request |
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187 | executes, with the exception of paths, which are being copied |
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188 | internally. Any memory libeio itself allocates will be freed after the |
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189 | finish callback has been called. If you want to manage all memory passed |
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190 | to libeio yourself you can use the low-level API. |
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191 | |
|
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192 | For example, to open a file, you could do this: |
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193 | |
|
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194 | static int |
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195 | file_open_done (eio_req *req) |
|
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196 | { |
|
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197 | if (req->result < 0) |
|
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198 | { |
|
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199 | /* open() returned -1 */ |
|
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200 | errno = req->errorno; |
|
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201 | perror ("open"); |
|
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202 | } |
|
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203 | else |
|
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204 | { |
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205 | int fd = req->result; |
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206 | /* now we have the new fd in fd */ |
|
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207 | } |
|
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208 | |
|
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209 | return 0; |
|
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210 | } |
|
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211 | |
|
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212 | /* the first three arguments are passed to open(2) */ |
|
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213 | /* the remaining are priority, callback and data */ |
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214 | if (!eio_open ("/etc/passwd", O_RDONLY, 0, 0, file_open_done, 0)) |
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215 | abort (); /* something ent wrong, we will all die!!! */ |
|
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216 | |
|
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217 | Note that you additionally need to call C<eio_poll> when the C<want_cb> |
|
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218 | indicates that requests are ready to be processed. |
|
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219 | |
|
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220 | =head2 AVAILABLE REQUESTS |
|
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221 | |
|
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222 | The following request functions are available. I<All> of them return the |
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223 | C<eio_req *> on success and C<0> on failure, and I<all> of them have the |
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224 | same three trailing arguments: C<pri>, C<cb> and C<data>. The C<cb> is |
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225 | mandatory, but in most cases, you pass in C<0> as C<pri> and C<0> or some |
|
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226 | custom data value as C<data>. |
|
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227 | |
|
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228 | =head3 POSIX API WRAPPERS |
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229 | |
|
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230 | These requests simply wrap the POSIX call of the same name, with the same |
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231 | arguments: |
|
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232 | |
|
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233 | =over 4 |
|
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234 | |
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235 | =item eio_open (const char *path, int flags, mode_t mode, int pri, eio_cb cb, void *data) |
|
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236 | |
|
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237 | =item eio_utime (const char *path, eio_tstamp atime, eio_tstamp mtime, int pri, eio_cb cb, void *data) |
|
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238 | |
|
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239 | =item eio_truncate (const char *path, off_t offset, int pri, eio_cb cb, void *data) |
|
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240 | |
|
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241 | =item eio_chown (const char *path, uid_t uid, gid_t gid, int pri, eio_cb cb, void *data) |
|
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242 | |
|
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243 | =item eio_chmod (const char *path, mode_t mode, int pri, eio_cb cb, void *data) |
|
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244 | |
|
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245 | =item eio_mkdir (const char *path, mode_t mode, int pri, eio_cb cb, void *data) |
|
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246 | |
|
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247 | =item eio_rmdir (const char *path, int pri, eio_cb cb, void *data) |
|
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248 | |
|
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249 | =item eio_unlink (const char *path, int pri, eio_cb cb, void *data) |
|
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250 | |
|
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251 | =item eio_readlink (const char *path, int pri, eio_cb cb, void *data) /* result=ptr2 allocated dynamically */ |
|
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252 | |
|
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253 | =item eio_stat (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
|
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254 | |
|
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255 | =item eio_lstat (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
|
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256 | |
|
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257 | =item eio_statvfs (const char *path, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
|
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258 | |
|
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259 | =item eio_mknod (const char *path, mode_t mode, dev_t dev, int pri, eio_cb cb, void *data) |
|
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260 | |
|
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261 | =item eio_link (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
|
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262 | |
|
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263 | =item eio_symlink (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
|
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264 | |
|
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265 | =item eio_rename (const char *path, const char *new_path, int pri, eio_cb cb, void *data) |
|
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266 | |
|
|
267 | =item eio_msync (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) |
|
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268 | |
|
|
269 | =item eio_mlock (void *addr, size_t length, int pri, eio_cb cb, void *data) |
|
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270 | |
|
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271 | =item eio_mlockall (int flags, int pri, eio_cb cb, void *data) |
|
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272 | |
|
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273 | =item eio_close (int fd, int pri, eio_cb cb, void *data) |
|
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274 | |
|
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275 | =item eio_sync (int pri, eio_cb cb, void *data) |
|
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276 | |
|
|
277 | =item eio_fsync (int fd, int pri, eio_cb cb, void *data) |
|
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278 | |
|
|
279 | =item eio_fdatasync (int fd, int pri, eio_cb cb, void *data) |
|
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280 | |
|
|
281 | =item eio_futime (int fd, eio_tstamp atime, eio_tstamp mtime, int pri, eio_cb cb, void *data) |
|
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282 | |
|
|
283 | =item eio_ftruncate (int fd, off_t offset, int pri, eio_cb cb, void *data) |
|
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284 | |
|
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285 | =item eio_fchmod (int fd, mode_t mode, int pri, eio_cb cb, void *data) |
|
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286 | |
|
|
287 | =item eio_fchown (int fd, uid_t uid, gid_t gid, int pri, eio_cb cb, void *data) |
|
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288 | |
|
|
289 | =item eio_dup2 (int fd, int fd2, int pri, eio_cb cb, void *data) |
|
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290 | |
|
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291 | These have the same semantics as the syscall of the same name, their |
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292 | return value is available as C<< req->result >> later. |
|
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293 | |
|
|
294 | =item eio_read (int fd, void *buf, size_t length, off_t offset, int pri, eio_cb cb, void *data) |
|
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295 | |
|
|
296 | =item eio_write (int fd, void *buf, size_t length, off_t offset, int pri, eio_cb cb, void *data) |
|
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297 | |
|
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298 | These two requests are called C<read> and C<write>, but actually wrap |
|
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299 | C<pread> and C<pwrite>. On systems that lack these calls (such as cygwin), |
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300 | libeio uses lseek/read_or_write/lseek and a mutex to serialise the |
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301 | requests, so all these requests run serially and do not disturb each |
|
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302 | other. However, they still disturb the file offset while they run, so it's |
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303 | not safe to call these functions concurrently with non-libeio functions on |
|
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304 | the same fd on these systems. |
|
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305 | |
|
|
306 | Not surprisingly, pread and pwrite are not thread-safe on Darwin (OS/X), |
|
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307 | so it is advised not to submit multiple requests on the same fd on this |
|
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308 | horrible pile of garbage. |
|
|
309 | |
|
|
310 | =item eio_fstat (int fd, int pri, eio_cb cb, void *data) |
|
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311 | |
|
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312 | Stats a file - if C<< req->result >> indicates success, then you can |
|
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313 | access the C<struct stat>-like structure via C<< req->ptr2 >>: |
|
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314 | |
|
|
315 | EIO_STRUCT_STAT *statdata = (EIO_STRUCT_STAT *)req->ptr2; |
|
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316 | |
|
|
317 | =item eio_fstatvfs (int fd, int pri, eio_cb cb, void *data) /* stat buffer=ptr2 allocated dynamically */ |
|
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318 | |
|
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319 | Stats a filesystem - if C<< req->result >> indicates success, then you can |
|
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320 | access the C<struct statvfs>-like structure via C<< req->ptr2 >>: |
|
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321 | |
|
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322 | EIO_STRUCT_STATVFS *statdata = (EIO_STRUCT_STATVFS *)req->ptr2; |
|
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323 | |
|
|
324 | =back |
|
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325 | |
|
|
326 | =head3 READING DIRECTORIES |
|
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327 | |
|
|
328 | Reading directories sounds simple, but can be rather demanding, especially |
|
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329 | if you want to do stuff such as traversing a diretcory hierarchy or |
|
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330 | processing all files in a directory. Libeio can assist thess complex tasks |
|
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331 | with it's C<eio_readdir> call. |
|
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332 | |
|
|
333 | =over 4 |
|
|
334 | |
|
|
335 | =item eio_readdir (const char *path, int flags, int pri, eio_cb cb, void *data) |
|
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336 | |
|
|
337 | This is a very complex call. It basically reads through a whole directory |
|
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338 | (via the C<opendir>, C<readdir> and C<closedir> calls) and returns either |
|
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339 | the names or an array of C<struct eio_dirent>, depending on the C<flags> |
|
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340 | argument. |
|
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341 | |
|
|
342 | The C<< req->result >> indicates either the number of files found, or |
|
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343 | C<-1> on error. On success, zero-terminated names can be found as C<< req->ptr2 >>, |
|
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344 | and C<struct eio_dirents>, if requested by C<flags>, can be found via C<< |
|
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345 | req->ptr1 >>. |
|
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346 | |
|
|
347 | Here is an example that prints all the names: |
|
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348 | |
|
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349 | int i; |
|
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350 | char *names = (char *)req->ptr2; |
|
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351 | |
|
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352 | for (i = 0; i < req->result; ++i) |
|
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353 | { |
|
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354 | printf ("name #%d: %s\n", i, names); |
|
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355 | |
|
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356 | /* move to next name */ |
|
|
357 | names += strlen (names) + 1; |
|
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358 | } |
|
|
359 | |
|
|
360 | Pseudo-entries such as F<.> and F<..> are never returned by C<eio_readdir>. |
|
|
361 | |
|
|
362 | C<flags> can be any combination of: |
|
|
363 | |
|
|
364 | =over 4 |
|
|
365 | |
|
|
366 | =item EIO_READDIR_DENTS |
|
|
367 | |
|
|
368 | If this flag is specified, then, in addition to the names in C<ptr2>, |
|
|
369 | also an array of C<struct eio_dirent> is returned, in C<ptr1>. A C<struct |
|
|
370 | eio_dirent> looks like this: |
|
|
371 | |
|
|
372 | struct eio_dirent |
|
|
373 | { |
|
|
374 | int nameofs; /* offset of null-terminated name string in (char *)req->ptr2 */ |
|
|
375 | unsigned short namelen; /* size of filename without trailing 0 */ |
|
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376 | unsigned char type; /* one of EIO_DT_* */ |
|
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377 | signed char score; /* internal use */ |
|
|
378 | ino_t inode; /* the inode number, if available, otherwise unspecified */ |
|
|
379 | }; |
|
|
380 | |
|
|
381 | The only members you normally would access are C<nameofs>, which is the |
|
|
382 | byte-offset from C<ptr2> to the start of the name, C<namelen> and C<type>. |
|
|
383 | |
|
|
384 | C<type> can be one of: |
|
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385 | |
|
|
386 | C<EIO_DT_UNKNOWN> - if the type is not known (very common) and you have to C<stat> |
|
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387 | the name yourself if you need to know, |
|
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388 | one of the "standard" POSIX file types (C<EIO_DT_REG>, C<EIO_DT_DIR>, C<EIO_DT_LNK>, |
|
|
389 | C<EIO_DT_FIFO>, C<EIO_DT_SOCK>, C<EIO_DT_CHR>, C<EIO_DT_BLK>) |
|
|
390 | or some OS-specific type (currently |
|
|
391 | C<EIO_DT_MPC> - multiplexed char device (v7+coherent), |
|
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392 | C<EIO_DT_NAM> - xenix special named file, |
|
|
393 | C<EIO_DT_MPB> - multiplexed block device (v7+coherent), |
|
|
394 | C<EIO_DT_NWK> - HP-UX network special, |
|
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395 | C<EIO_DT_CMP> - VxFS compressed, |
|
|
396 | C<EIO_DT_DOOR> - solaris door, or |
|
|
397 | C<EIO_DT_WHT>). |
|
|
398 | |
|
|
399 | This example prints all names and their type: |
|
|
400 | |
|
|
401 | int i; |
|
|
402 | struct eio_dirent *ents = (struct eio_dirent *)req->ptr1; |
|
|
403 | char *names = (char *)req->ptr2; |
|
|
404 | |
|
|
405 | for (i = 0; i < req->result; ++i) |
|
|
406 | { |
|
|
407 | struct eio_dirent *ent = ents + i; |
|
|
408 | char *name = names + ent->nameofs; |
|
|
409 | |
|
|
410 | printf ("name #%d: %s (type %d)\n", i, name, ent->type); |
|
|
411 | } |
|
|
412 | |
|
|
413 | =item EIO_READDIR_DIRS_FIRST |
|
|
414 | |
|
|
415 | When this flag is specified, then the names will be returned in an order |
|
|
416 | where likely directories come first, in optimal C<stat> order. This is |
|
|
417 | useful when you need to quickly find directories, or you want to find all |
|
|
418 | directories while avoiding to stat() each entry. |
|
|
419 | |
|
|
420 | If the system returns type information in readdir, then this is used |
|
|
421 | to find directories directly. Otherwise, likely directories are names |
|
|
422 | beginning with ".", or otherwise names with no dots, of which names with |
|
|
423 | short names are tried first. |
|
|
424 | |
|
|
425 | =item EIO_READDIR_STAT_ORDER |
|
|
426 | |
|
|
427 | When this flag is specified, then the names will be returned in an order |
|
|
428 | suitable for stat()'ing each one. That is, when you plan to stat() |
|
|
429 | all files in the given directory, then the returned order will likely |
|
|
430 | be fastest. |
|
|
431 | |
|
|
432 | If both this flag and C<EIO_READDIR_DIRS_FIRST> are specified, then |
|
|
433 | the likely dirs come first, resulting in a less optimal stat order. |
|
|
434 | |
|
|
435 | =item EIO_READDIR_FOUND_UNKNOWN |
|
|
436 | |
|
|
437 | This flag should not be specified when calling C<eio_readdir>. Instead, |
|
|
438 | it is being set by C<eio_readdir> (you can access the C<flags> via C<< |
|
|
439 | req->int1 >>, when any of the C<type>'s found were C<EIO_DT_UNKNOWN>. The |
|
|
440 | absense of this flag therefore indicates that all C<type>'s are known, |
|
|
441 | which can be used to speed up some algorithms. |
|
|
442 | |
|
|
443 | A typical use case would be to identify all subdirectories within a |
|
|
444 | directory - you would ask C<eio_readdir> for C<EIO_READDIR_DIRS_FIRST>. If |
|
|
445 | then this flag is I<NOT> set, then all the entries at the beginning of the |
|
|
446 | returned array of type C<EIO_DT_DIR> are the directories. Otherwise, you |
|
|
447 | should start C<stat()>'ing the entries starting at the beginning of the |
|
|
448 | array, stopping as soon as you found all directories (the count can be |
|
|
449 | deduced by the link count of the directory). |
|
|
450 | |
|
|
451 | =back |
|
|
452 | |
|
|
453 | =back |
|
|
454 | |
|
|
455 | =head3 OS-SPECIFIC CALL WRAPPERS |
|
|
456 | |
|
|
457 | These wrap OS-specific calls (usually Linux ones), and might or might not |
|
|
458 | be emulated on other operating systems. Calls that are not emulated will |
|
|
459 | return C<-1> and set C<errno> to C<ENOSYS>. |
|
|
460 | |
|
|
461 | =over 4 |
|
|
462 | |
|
|
463 | =item eio_sendfile (int out_fd, int in_fd, off_t in_offset, size_t length, int pri, eio_cb cb, void *data) |
|
|
464 | |
|
|
465 | Wraps the C<sendfile> syscall. The arguments follow the Linux version, but |
|
|
466 | libeio supports and will use similar calls on FreeBSD, HP/UX, Solaris and |
|
|
467 | Darwin. |
|
|
468 | |
|
|
469 | If the OS doesn't support some sendfile-like call, or the call fails, |
|
|
470 | indicating support for the given file descriptor type (for example, |
|
|
471 | Linux's sendfile might not support file to file copies), then libeio will |
|
|
472 | emulate the call in userspace, so there are almost no limitations on its |
|
|
473 | use. |
|
|
474 | |
|
|
475 | =item eio_readahead (int fd, off_t offset, size_t length, int pri, eio_cb cb, void *data) |
|
|
476 | |
|
|
477 | Calls C<readahead(2)>. If the syscall is missing, then the call is |
|
|
478 | emulated by simply reading the data (currently in 64kiB chunks). |
|
|
479 | |
|
|
480 | =item eio_sync_file_range (int fd, off_t offset, size_t nbytes, unsigned int flags, int pri, eio_cb cb, void *data) |
|
|
481 | |
|
|
482 | Calls C<sync_file_range>. If the syscall is missing, then this is the same |
|
|
483 | as calling C<fdatasync>. |
|
|
484 | |
|
|
485 | =back |
|
|
486 | |
|
|
487 | =head3 LIBEIO-SPECIFIC REQUESTS |
|
|
488 | |
|
|
489 | These requests are specific to libeio and do not correspond to any OS call. |
|
|
490 | |
|
|
491 | =over 4 |
|
|
492 | |
|
|
493 | =item eio_mtouch (void *addr, size_t length, int flags, int pri, eio_cb cb, void *data) |
|
|
494 | |
|
|
495 | Reads (C<flags == 0>) or modifies (C<flags == EIO_MT_MODIFY) the given |
|
|
496 | memory area, page-wise, that is, it reads (or reads and writes back) the |
|
|
497 | first octet of every page that spans the memory area. |
|
|
498 | |
|
|
499 | This can be used to page in some mmapped file, or dirty some pages. Note |
|
|
500 | that dirtying is an unlocked read-write access, so races can ensue when |
|
|
501 | the some other thread modifies the data stored in that memory area. |
|
|
502 | |
|
|
503 | =item eio_custom (void (*)(eio_req *) execute, int pri, eio_cb cb, void *data) |
|
|
504 | |
|
|
505 | Executes a custom request, i.e., a user-specified callback. |
|
|
506 | |
|
|
507 | The callback gets the C<eio_req *> as parameter and is expected to read |
|
|
508 | and modify any request-specific members. Specifically, it should set C<< |
|
|
509 | req->result >> to the result value, just like other requests. |
|
|
510 | |
|
|
511 | Here is an example that simply calls C<open>, like C<eio_open>, but it |
|
|
512 | uses the C<data> member as filename and uses a hardcoded C<O_RDONLY>. If |
|
|
513 | you want to pass more/other parameters, you either need to pass some |
|
|
514 | struct or so via C<data> or provide your own wrapper using the low-level |
|
|
515 | API. |
|
|
516 | |
|
|
517 | static int |
|
|
518 | my_open_done (eio_req *req) |
|
|
519 | { |
|
|
520 | int fd = req->result; |
|
|
521 | |
|
|
522 | return 0; |
|
|
523 | } |
|
|
524 | |
|
|
525 | static void |
|
|
526 | my_open (eio_req *req) |
|
|
527 | { |
|
|
528 | req->result = open (req->data, O_RDONLY); |
|
|
529 | } |
|
|
530 | |
|
|
531 | eio_custom (my_open, 0, my_open_done, "/etc/passwd"); |
|
|
532 | |
|
|
533 | =item eio_busy (eio_tstamp delay, int pri, eio_cb cb, void *data) |
|
|
534 | |
|
|
535 | This is a a request that takes C<delay> seconds to execute, but otherwise |
|
|
536 | does nothing - it simply puts one of the worker threads to sleep for this |
|
|
537 | long. |
|
|
538 | |
|
|
539 | This request can be used to artificially increase load, e.g. for debugging |
|
|
540 | or benchmarking reasons. |
|
|
541 | |
|
|
542 | =item eio_nop (int pri, eio_cb cb, void *data) |
|
|
543 | |
|
|
544 | This request does nothing, except go through the whole request cycle. This |
|
|
545 | can be used to measure latency or in some cases to simplify code, but is |
|
|
546 | not really of much use. |
|
|
547 | |
|
|
548 | =back |
|
|
549 | |
|
|
550 | =head3 GROUPING AND LIMITING REQUESTS |
|
|
551 | |
|
|
552 | #TODO |
|
|
553 | |
|
|
554 | /*****************************************************************************/ |
|
|
555 | /* groups */ |
|
|
556 | |
|
|
557 | eio_req *eio_grp (eio_cb cb, void *data); |
|
|
558 | void eio_grp_feed (eio_req *grp, void (*feed)(eio_req *req), int limit); |
|
|
559 | void eio_grp_limit (eio_req *grp, int limit); |
|
|
560 | void eio_grp_add (eio_req *grp, eio_req *req); |
|
|
561 | void eio_grp_cancel (eio_req *grp); /* cancels all sub requests but not the group */ |
|
|
562 | |
|
|
563 | |
|
|
564 | =back |
|
|
565 | |
|
|
566 | |
|
|
567 | =head1 LOW LEVEL REQUEST API |
|
|
568 | |
|
|
569 | #TODO |
|
|
570 | |
|
|
571 | |
|
|
572 | =head1 ANATOMY AND LIFETIME OF AN EIO REQUEST |
|
|
573 | |
|
|
574 | A request is represented by a structure of type C<eio_req>. To initialise |
|
|
575 | it, clear it to all zero bytes: |
|
|
576 | |
|
|
577 | eio_req req; |
|
|
578 | |
|
|
579 | memset (&req, 0, sizeof (req)); |
|
|
580 | |
|
|
581 | A more common way to initialise a new C<eio_req> is to use C<calloc>: |
|
|
582 | |
|
|
583 | eio_req *req = calloc (1, sizeof (*req)); |
|
|
584 | |
|
|
585 | In either case, libeio neither allocates, initialises or frees the |
|
|
586 | C<eio_req> structure for you - it merely uses it. |
|
|
587 | |
|
|
588 | zero |
|
|
589 | |
|
|
590 | #TODO |
|
|
591 | |
138 | =head2 CONFIGURATION |
592 | =head2 CONFIGURATION |
139 | |
593 | |
140 | The functions in this section can sometimes be useful, but the default |
594 | The functions in this section can sometimes be useful, but the default |
141 | configuration will do in most case, so you should skip this section on |
595 | configuration will do in most case, so you should skip this section on |
142 | first reading. |
596 | first reading. |
… | |
… | |
185 | =item eio_set_max_idle (unsigned int nthreads) |
639 | =item eio_set_max_idle (unsigned int nthreads) |
186 | |
640 | |
187 | Libeio uses threads internally to handle most requests, and will start and stop threads on demand. |
641 | Libeio uses threads internally to handle most requests, and will start and stop threads on demand. |
188 | |
642 | |
189 | This call can be used to limit the number of idle threads (threads without |
643 | This call can be used to limit the number of idle threads (threads without |
190 | work to do): libeio will keep some threads idle in preperation for more |
644 | work to do): libeio will keep some threads idle in preparation for more |
191 | requests, but never longer than C<nthreads> threads. |
645 | requests, but never longer than C<nthreads> threads. |
192 | |
646 | |
193 | In addition to this, libeio will also stop threads when they are idle for |
647 | In addition to this, libeio will also stop threads when they are idle for |
194 | a few seconds, regardless of this setting. |
648 | a few seconds, regardless of this setting. |
195 | |
649 | |
… | |
… | |
213 | Returns the number of pending requests, i.e. requests that have been |
667 | Returns the number of pending requests, i.e. requests that have been |
214 | executed and have results, but have not been finished yet by a call to |
668 | executed and have results, but have not been finished yet by a call to |
215 | C<eio_poll>). |
669 | C<eio_poll>). |
216 | |
670 | |
217 | =back |
671 | =back |
218 | |
|
|
219 | |
|
|
220 | =head1 ANATOMY OF AN EIO REQUEST |
|
|
221 | |
|
|
222 | #TODO |
|
|
223 | |
|
|
224 | |
|
|
225 | =head1 HIGH LEVEL REQUEST API |
|
|
226 | |
|
|
227 | #TODO |
|
|
228 | |
|
|
229 | =back |
|
|
230 | |
|
|
231 | |
|
|
232 | =head1 LOW LEVEL REQUEST API |
|
|
233 | |
|
|
234 | #TODO |
|
|
235 | |
672 | |
236 | =head1 EMBEDDING |
673 | =head1 EMBEDDING |
237 | |
674 | |
238 | Libeio can be embedded directly into programs. This functionality is not |
675 | Libeio can be embedded directly into programs. This functionality is not |
239 | documented and not (yet) officially supported. |
676 | documented and not (yet) officially supported. |