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112 lines
3.2 KiB
Markdown
112 lines
3.2 KiB
Markdown
ref-struct
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==========
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### Create ABI-compliant "[struct][]" instances on top of Buffers
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[](https://travis-ci.org/TooTallNate/ref-struct)
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[](https://ci.appveyor.com/project/TooTallNate/ref-struct)
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This module offers a "struct" implementation on top of Node.js Buffers
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using the ref "type" interface.
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Installation
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------------
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Install with `npm`:
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``` bash
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$ npm install ref-struct
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```
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Examples
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--------
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Say you wanted to emulate the `timeval` struct from the stdlib:
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``` c
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struct timeval {
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time_t tv_sec; /* seconds since Jan. 1, 1970 */
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suseconds_t tv_usec; /* and microseconds */
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};
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```
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``` js
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var ref = require('ref')
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var StructType = require('ref-struct')
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// define the time types
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var time_t = ref.types.long
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var suseconds_t = ref.types.long
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// define the "timeval" struct type
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var timeval = StructType({
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tv_sec: time_t,
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tv_usec: suseconds_t
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})
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// now we can create instances of it
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var tv = new timeval
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```
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#### With `node-ffi`
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This gets very powerful when combined with `node-ffi` to invoke C functions:
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``` js
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var ffi = require('ffi')
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var tv = new timeval
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gettimeofday(tv.ref(), null)
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```
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#### Progressive API
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You can build up a Struct "type" incrementally (useful when interacting with a
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parser) using the `defineProperty()` function. But as soon as you _create_ an
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instance of the struct type, then the struct type is finalized, and no more
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properties may be added to it.
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``` js
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var ref = require('ref')
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var StructType = require('ref-struct')
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var MyStruct = StructType()
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MyStruct.defineProperty('width', ref.types.int)
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MyStruct.defineProperty('height', ref.types.int)
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var i = new MyStruct({ width: 5, height: 10 })
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MyStruct.defineProperty('weight', ref.types.int)
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// AssertionError: an instance of this Struct type has already been created, cannot add new "fields" anymore
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// at Function.defineProperty (/Users/nrajlich/ref-struct/lib/struct.js:180:3)
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```
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License
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-------
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(The MIT License)
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Copyright (c) 2012 Nathan Rajlich <nathan@tootallnate.net>
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Permission is hereby granted, free of charge, to any person obtaining
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a copy of this software and associated documentation files (the
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'Software'), to deal in the Software without restriction, including
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without limitation the rights to use, copy, modify, merge, publish,
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distribute, sublicense, and/or sell copies of the Software, and to
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permit persons to whom the Software is furnished to do so, subject to
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the following conditions:
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The above copyright notice and this permission notice shall be
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included in all copies or substantial portions of the Software.
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THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND,
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
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MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
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IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
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CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
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TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
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SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
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[struct]: http://wikipedia.org/wiki/Struct_(C_programming_language)
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