xfermem.h
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
/*
xfermem: unidirectional fast pipe
copyright ?-2006 by the mpg123 project - free software under the terms of the LGPL 2.1
see COPYING and AUTHORS files in distribution or http://mpg123.org
initially written by Oliver Fromme
old timestamp: Sat Mar 29 04:41:34 MET 1997
This is a stand-alone module which implements a unidirectional,
fast pipe using mmap(). Its primary use is to transfer large
amounts of data from a parent process to its child process,
with a buffer in between which decouples blocking conditions
on both sides. Control information is transferred between the
processes through a socketpair. See xftest.c for an example on
how to use this module.
note: xftest not there anymore
*/
#ifndef _XFERMEM_H_
#define _XFERMEM_H_
#include "compat.h"
typedef struct {
size_t freeindex; /* [W] next free index */
size_t readindex; /* [R] next index to read */
int fd[2];
char *data;
char *metadata;
size_t size;
size_t metasize;
} txfermem;
/*
* [W] -- May be written to by the writing process only!
* [R] -- May be written to by the reading process only!
* All other entries are initialized once.
*/
void xfermem_init (txfermem **xf, size_t bufsize, size_t msize, size_t skipbuf);
void xfermem_init_writer (txfermem *xf);
void xfermem_init_reader (txfermem *xf);
size_t xfermem_get_freespace (txfermem *xf);
size_t xfermem_get_usedspace (txfermem *xf);
/* Unless otherwise noted, each command demands a reponse if issued from the
writer. The reader does not expect responses, only orders. */
enum xf_cmd_code
{
XF_CMD_PING = 1 /**< Wake up and give a response, not changing any state. */
, XF_CMD_PONG /**< The response to a ping. */
, XF_CMD_DATA /**< Re-check the amount of data available without response. */
, XF_CMD_TERMINATE /**< Stop operation. */
, XF_CMD_DROP /**< Drop current buffer contents. */
, XF_CMD_DRAIN /**< Consume current buffer contents now. */
, XF_CMD_PAUSE /**< Pause operation, wait for next command. */
, XF_CMD_CONTINUE /**< Continue operation. */
, XF_CMD_IGNLOW /**< Ignore situation with low buffer fill. */
, XF_CMD_OK /**< Response from reader: Operation succeeded. */
, XF_CMD_ERROR /**< Response from reader: Operation failed. */
, XF_CMD_CUSTOM1 /**< Some custom command to be filled with meaning. */
, XF_CMD_CUSTOM2 /**< Some custom command to be filled with meaning. */
, XF_CMD_CUSTOM3 /**< Some custom command to be filled with meaning. */
, XF_CMD_CUSTOM4 /**< Some custom command to be filled with meaning. */
, XF_CMD_CUSTOM5 /**< Some custom command to be filled with meaning. */
, XF_CMD_CUSTOM6 /**< Some custom command to be filled with meaning. */
, XF_CMD_CUSTOM7 /**< Some custom command to be filled with meaning. */
, XF_CMD_CUSTOM8 /**< Some custom command to be filled with meaning. */
};
#define XF_WRITER 0
#define XF_READER 1
int xfermem_getcmd(int fd, int block);
int xfermem_getcmds(int fd, int block, byte* cmds, int count);
int xfermem_putcmd(int fd, byte cmd);
int xfermem_writer_block(txfermem *xf);
/* returns TRUE for being interrupted */
int xfermem_write(txfermem *xf, void *buffer, size_t bytes);
void xfermem_done (txfermem *xf);
#define xfermem_done_writer xfermem_init_reader
#define xfermem_done_reader xfermem_init_writer
#endif