bnoordhuis / Node Mmap
Licence: mit
mmap(2) bindings for node.js
Stars: ✭ 51
node-mmap
mmap(2) bindings for node.js - stop slurping, start mapping.
** This module is no longer maintained. **
Installing
Through npm:
npm install mmap
Or compile it from source with this one-liner:
node-waf configure build install
Usage
buffer = mmap.map(n_bytes, protection, flags, fd, offset);
| n_bytes | The number of bytes to map into memory. |
| protection | Memory protection: either PROT_NONE or a bitwise OR of PROT_READ, PROT_WRITE and PROT_EXEC. |
| flags | Flags: either MAP_SHARED or MAP_PRIVATE. |
| fd | File descriptor. |
| offset | File offset. Must be either zero or a multiple of mmap.PAGESIZE. |
See the man page for more details.
Examples
Map a file into memory:
fs = require('fs'), mmap = require('mmap');
fd = fs.openSync('/path/to/file', 'r');
size = fs.fstatSync(fd).size;
buffer = mmap.map(size, mmap.PROT_READ, mmap.MAP_SHARED, fd, 0);
// calculate faux checksum
var checksum = 0;
for (var i = 0; i < buffer.length; i++) {
checksum ^= buffer[i];
}
The file is automatically unmapped when the buffer object is garbage collected.
Bugs and limitations
-
Specifying the memory address is not implemented. I couldn't think of a reason why you would want to do that from JavaScript. Convince me otherwise. :-)
-
Reading from and writing to memory-mapped files is a potentially blocking operation. Do not use this module in performance critical code. Better yet, don't use this module at all.
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