diff options
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/ext_ffi.html | 11 | ||||
| -rw-r--r-- | doc/ext_ffi_api.html | 25 | ||||
| -rw-r--r-- | doc/ext_ffi_semantics.html | 41 |
3 files changed, 54 insertions, 23 deletions
diff --git a/doc/ext_ffi.html b/doc/ext_ffi.html index e8e2a62b..f496b51b 100644 --- a/doc/ext_ffi.html +++ b/doc/ext_ffi.html | |||
| @@ -73,8 +73,8 @@ The FFI library is tightly integrated into LuaJIT (it's not available | |||
| 73 | as a separate module). The code generated by the JIT-compiler for | 73 | as a separate module). The code generated by the JIT-compiler for |
| 74 | accesses to C data structures from Lua code is on par with the | 74 | accesses to C data structures from Lua code is on par with the |
| 75 | code a C compiler would generate. Calls to C functions can | 75 | code a C compiler would generate. Calls to C functions can |
| 76 | be inlined in the JIT-compiled code, unlike calls to functions bound | 76 | be inlined in JIT-compiled code, unlike calls to functions bound via |
| 77 | via the classic Lua/C API. | 77 | the classic Lua/C API. |
| 78 | </p> | 78 | </p> |
| 79 | <p> | 79 | <p> |
| 80 | This page gives a short introduction to the usage of the FFI library. | 80 | This page gives a short introduction to the usage of the FFI library. |
| @@ -253,14 +253,17 @@ would consume 40 Megabytes in plain Lua (on x64). | |||
| 253 | Next, performance: the pure Lua version runs in 9.57 seconds (52.9 | 253 | Next, performance: the pure Lua version runs in 9.57 seconds (52.9 |
| 254 | seconds with the Lua interpreter) and the FFI version runs in 0.48 | 254 | seconds with the Lua interpreter) and the FFI version runs in 0.48 |
| 255 | seconds on my machine (YMMV). That's a factor of 20x faster (110x | 255 | seconds on my machine (YMMV). That's a factor of 20x faster (110x |
| 256 | faster than with plain Lua). | 256 | faster than the Lua interpreter). |
| 257 | </p> | 257 | </p> |
| 258 | <p style="font-size: 8pt;"> | 258 | <p style="font-size: 8pt;"> |
| 259 | The avid reader may notice that converting the pure Lua version over | 259 | The avid reader may notice that converting the pure Lua version over |
| 260 | to use array indexes for the colors (<tt>[1]</tt> instead of | 260 | to use array indexes for the colors (<tt>[1]</tt> instead of |
| 261 | <tt>.red</tt>, <tt>[2]</tt> instead of <tt>.green</tt> etc.) ought to | 261 | <tt>.red</tt>, <tt>[2]</tt> instead of <tt>.green</tt> etc.) ought to |
| 262 | be more compact and faster. This is certainly true (by a factor of | 262 | be more compact and faster. This is certainly true (by a factor of |
| 263 | ~1.7x), but the resulting code would be less idiomatic and rather | 263 | ~1.7x). Switching to a struct-of-arrays would help, too. |
| 264 | </p> | ||
| 265 | <p style="font-size: 8pt;"> | ||
| 266 | However the resulting code would be less idiomatic and rather | ||
| 264 | error-prone. And it still doesn't get even close to the performance of | 267 | error-prone. And it still doesn't get even close to the performance of |
| 265 | the FFI version of the code. Also, high-level data structures cannot | 268 | the FFI version of the code. Also, high-level data structures cannot |
| 266 | be easily passed to other C functions, especially I/O functions, | 269 | be easily passed to other C functions, especially I/O functions, |
diff --git a/doc/ext_ffi_api.html b/doc/ext_ffi_api.html index f985d965..f0c4de90 100644 --- a/doc/ext_ffi_api.html +++ b/doc/ext_ffi_api.html | |||
| @@ -195,23 +195,10 @@ require the <tt>nelem</tt> argument. The second syntax uses a ctype as | |||
| 195 | a constructor and is otherwise fully equivalent. | 195 | a constructor and is otherwise fully equivalent. |
| 196 | </p> | 196 | </p> |
| 197 | <p> | 197 | <p> |
| 198 | The <tt>init</tt> arguments provide optional initializers. The created | 198 | The cdata object is initialized according to the |
| 199 | cdata object is filled with zero bytes if no initializers are given. | 199 | <a href="ext_ffi_semantics.html#init">rules for initializers</a>, |
| 200 | Scalar types accept a single initializer. Aggregates can either be | 200 | using the optional <tt>init</tt> arguments. Excess initializers cause |
| 201 | initialized with a flat list of initializers or a single aggregate | 201 | an error. |
| 202 | initializer (see the <a href="ext_ffi_semantics.html#convert">C type | ||
| 203 | conversion rules</a>). Excess initializers cause an error. | ||
| 204 | </p> | ||
| 205 | <p> | ||
| 206 | If a single initializer is given for an array, it's repeated for all | ||
| 207 | remaining elements. This doesn't happen if two or more initializers | ||
| 208 | are given — all uninitialized elements are filled with zero | ||
| 209 | bytes. The fields of a <tt>struct</tt> are initialized in the order of | ||
| 210 | their declaration. Uninitialized fields are filled with zero bytes. | ||
| 211 | Only the first field of <tt>union</tt> can be initialized with a flat | ||
| 212 | initializer. Elements or fields which are aggregates themselves are | ||
| 213 | initialized with a <em>single</em> <tt>init</tt> argument, but this | ||
| 214 | may be an aggregate initializer of course. | ||
| 215 | </p> | 202 | </p> |
| 216 | <p> | 203 | <p> |
| 217 | Performance notice: if you want to create many objects of one kind, | 204 | Performance notice: if you want to create many objects of one kind, |
| @@ -357,8 +344,8 @@ order of arguments! | |||
| 357 | <h3 id="ffi_abi"><tt>status = ffi.abi(param)</tt></h3> | 344 | <h3 id="ffi_abi"><tt>status = ffi.abi(param)</tt></h3> |
| 358 | <p> | 345 | <p> |
| 359 | Returns <tt>true</tt> if <tt>param</tt> (a Lua string) applies for the | 346 | Returns <tt>true</tt> if <tt>param</tt> (a Lua string) applies for the |
| 360 | target ABI (Application Binary Interface). Otherwise returns | 347 | target ABI (Application Binary Interface). Returns <tt>false</tt> |
| 361 | <tt>false</tt>. The following parameters are currently defined: | 348 | otherwise. The following parameters are currently defined: |
| 362 | </p> | 349 | </p> |
| 363 | <table class="abitable"> | 350 | <table class="abitable"> |
| 364 | <tr class="abihead"> | 351 | <tr class="abihead"> |
diff --git a/doc/ext_ffi_semantics.html b/doc/ext_ffi_semantics.html index 598d44c9..4a1b6c11 100644 --- a/doc/ext_ffi_semantics.html +++ b/doc/ext_ffi_semantics.html | |||
| @@ -70,6 +70,47 @@ TODO | |||
| 70 | TODO | 70 | TODO |
| 71 | </p> | 71 | </p> |
| 72 | 72 | ||
| 73 | <h2 id="init">Initializers</h2> | ||
| 74 | <p> | ||
| 75 | Creating a cdata object with <a href="ffi_ext_api.html#ffi_new">ffi.new()</a> | ||
| 76 | or the equivalent constructor syntax always initializes its contents, | ||
| 77 | too. Different rules apply, depending on the number of optional | ||
| 78 | initializers and the C types involved: | ||
| 79 | </p> | ||
| 80 | <ul> | ||
| 81 | <li>If no initializers are given, the object is filled with zero bytes.</li> | ||
| 82 | |||
| 83 | <li>Scalar types (numbers and pointers) accept a single initializer. | ||
| 84 | The standard <a href="#convert">C type conversion rules</a> | ||
| 85 | apply.</li> | ||
| 86 | |||
| 87 | <li>Valarrays (complex numbers and vectors) are treated like scalars | ||
| 88 | when a single initializer is given. Otherwise they are treated like | ||
| 89 | regular arrays.</li> | ||
| 90 | |||
| 91 | <li>Aggregate types (arrays and structs) accept either a single | ||
| 92 | compound initializer (Lua table or string) or a flat list of | ||
| 93 | initializers.</li> | ||
| 94 | |||
| 95 | <li>The elements of an array are initialized, starting at index zero. | ||
| 96 | If a single initializer is given for an array, it's repeated for all | ||
| 97 | remaining elements. This doesn't happen if two or more initializers | ||
| 98 | are given: all remaining uninitialized elements are filled with zero | ||
| 99 | bytes.</li> | ||
| 100 | |||
| 101 | <li>The fields of a <tt>struct</tt> are initialized in the order of | ||
| 102 | their declaration. Uninitialized fields are filled with zero | ||
| 103 | bytes.</li> | ||
| 104 | |||
| 105 | <li>Only the first field of a <tt>union</tt> can be initialized with a | ||
| 106 | flat initializer.</li> | ||
| 107 | |||
| 108 | <li>Elements or fields which are aggregates themselves are initialized | ||
| 109 | with a <em>single</em> initializer, but this may be a compound | ||
| 110 | initializer or a compatible aggregate, of course.</li> | ||
| 111 | |||
| 112 | </ul> | ||
| 113 | |||
| 73 | <h2 id="clib">C Library Namespaces</h2> | 114 | <h2 id="clib">C Library Namespaces</h2> |
| 74 | <p> | 115 | <p> |
| 75 | A C library namespace is a special kind of object which allows | 116 | A C library namespace is a special kind of object which allows |
