libburnia/libisofs
2
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

Add a ring buffer implementation.

Browse Source 
This is intented to replace the pipe between the writer and reader 
threads. That way we can have a much better control of cancelation 
situations. Still to be optimized.
This commit is contained in:
Vreixo Formoso 2007-12-23 02:24:21 +01:00
parent 9ec475a900
commit 94e687d9d3
6 changed files with 463 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
.bzrignore
View File

@ -29,3 +29,4 @@ demo/cat
demo/tree
demo/ecma119tree
demo/iso
demo/catbuffer

8
Makefile.am
View File

@ -36,7 +36,8 @@ src_libisofs_la_SOURCES = \
src/ecma119.c \
src/ecma119_tree.h \
src/ecma119_tree.c \
src/writer.h
src/writer.h \
src/buffer.c
libinclude_HEADERS = \
src/libisofs.h
@ -46,6 +47,7 @@ libinclude_HEADERS = \
noinst_PROGRAMS = \
demo/lsl \
demo/cat \
demo/catbuffer \
demo/tree \
demo/ecma119tree \
demo/iso
@ -58,6 +60,10 @@ demo_cat_CPPFLAGS = -Isrc
demo_cat_LDADD = $(src_libisofs_la_OBJECTS) $(THREAD_LIBS)
demo_cat_SOURCES = demo/cat.c
demo_catbuffer_CPPFLAGS = -Isrc
demo_catbuffer_LDADD = $(src_libisofs_la_OBJECTS) $(THREAD_LIBS)
demo_catbuffer_SOURCES = demo/cat_buffer.c
demo_tree_CPPFLAGS = -Isrc
demo_tree_LDADD = $(src_libisofs_la_OBJECTS) $(THREAD_LIBS)
demo_tree_SOURCES = demo/tree.c

126
demo/cat_buffer.c Normal file
View File

@ -0,0 +1,126 @@
/*
* Copyright (c) 2007 Vreixo Formoso
*
* This file is part of the libisofs project; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation. See COPYING file for details.
*/
#include "libisofs.h"
#include "buffer.h"
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
/*
* Little test program that reads a file and outputs it to stdout, using
* the libisofs ring buffer as intermediate memory
*/
struct th_data {
IsoRingBuffer *rbuf;
char *path;
};
#define WRITE_CHUNK 2048
#define READ_CHUNK 2048
static
void *write_function(void *arg)
{
ssize_t bytes;
int res;
unsigned char tmp[WRITE_CHUNK];
struct th_data *data = (struct th_data *) arg;
int fd = open(data->path, O_RDONLY);
if (fd < 0) {
fprintf(stderr, "Writer thread error: Can't open file");
iso_ring_buffer_writer_close(data->rbuf);
pthread_exit(NULL);
}
res = 1;
while ( (bytes = read(fd, tmp, WRITE_CHUNK)) > 0 ) {
res = iso_ring_buffer_write(data->rbuf, tmp, bytes);
if (res <= 0) {
break;
}
/* To test premature reader exit >>>>>>>>>>>
iso_ring_buffer_writer_close(data->rbuf);
pthread_exit(NULL);
<<<<<<<<<<<<<<<<<<<<<<<<< */
// if (rand() > 2000000000) {
// fprintf(stderr, "Writer sleeping\n");
// sleep(1);
// }
}
fprintf(stderr, "Writer finish: %d\n", res);
close(fd);
iso_ring_buffer_writer_close(data->rbuf);
pthread_exit(NULL);
}
static
void *read_function(void *arg)
{
unsigned char tmp[READ_CHUNK];
int res = 1;
struct th_data *data = (struct th_data *) arg;
while ( (res = iso_ring_buffer_read(data->rbuf, tmp, READ_CHUNK)) > 0 ) {
write(1, tmp, READ_CHUNK);
/* To test premature reader exit >>>>>>>>>>>
iso_ring_buffer_reader_close(data->rbuf);
pthread_exit(NULL);
<<<<<<<<<<<<<<<<<<<<<<<<< */
// if (rand() > 2000000000) {
// fprintf(stderr, "Reader sleeping\n");
// sleep(1);
// }
}
fprintf(stderr, "Reader finish: %d\n", res);
iso_ring_buffer_reader_close(data->rbuf);
pthread_exit(NULL);
}
int main(int argc, char **argv)
{
int res;
struct th_data data;
pthread_t reader;
pthread_t writer;
if (argc != 2) {
fprintf(stderr, "Usage: catbuffer /path/to/file\n");
return 1;
}
res = iso_ring_buffer_new(&data.rbuf);
if (res < 0) {
fprintf(stderr, "Can't create buffer\n");
return 1;
}
data.path = argv[1];
res = pthread_create(&writer, NULL, write_function, (void *) &data);
res = pthread_create(&reader, NULL, read_function, (void *) &data);
pthread_join(writer, NULL);
pthread_join(reader, NULL);
fprintf(stderr, "Buffer was %d times full and %d times empty.\n",
iso_ring_buffer_get_times_full(data.rbuf),
iso_ring_buffer_get_times_empty(data.rbuf));
free(data.rbuf);
return 0;
}

245
src/buffer.c Normal file
View File

@ -0,0 +1,245 @@
/*
* Copyright (c) 2007 Vreixo Formoso
*
* This file is part of the libisofs project; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation. See COPYING file for details.
*/
/*
* Synchronized ring buffer, works with a writer thread and a read thread.
*
* TODO things to optimize
* - write/read at the end of buffer requires a second mutex_lock, even if
* there's enought space/data at the beginning
* - pre-buffer for writes < BLOCK_SIZE
*
*/
#include "buffer.h"
#include "error.h"
#include <pthread.h>
#include <string.h>
#define BUFFER_CAPACITY BLOCK_SIZE * BUFFER_SIZE
#ifndef MIN
# define MIN(a, b) (((a) < (b)) ? (a) : (b))
#endif
struct iso_ring_buffer {
uint8_t buf[BLOCK_SIZE * BUFFER_SIZE];
/*
* Number of bytes available.
*/
size_t size;
/* position for reading and writing, offset from buf */
size_t rpos;
size_t wpos;
/* flags to report if read or writer threads ends execution */
unsigned int rend:1;
unsigned int wend:1;
/* just for statistical purposes */
unsigned int times_full;
unsigned int times_empty;
pthread_mutex_t mutex;
pthread_cond_t empty;
pthread_cond_t full;
};
/**
* Create a new buffer.
*
* The created buffer can be freed with free(3)
*
* @return
* 1 success, < 0 error
*/
int iso_ring_buffer_new(IsoRingBuffer **rbuf)
{
IsoRingBuffer *buffer;
if (rbuf == NULL) {
return ISO_NULL_POINTER;
}
buffer = malloc(sizeof(IsoRingBuffer));
if (buffer == NULL) {
return ISO_MEM_ERROR;
}
buffer->size = 0;
buffer->wpos = 0;
buffer->rpos = 0;
buffer->times_full = 0;
buffer->times_empty = 0;
buffer->rend = buffer->wend = 0;
/* init mutex and waiting queues */
pthread_mutex_init(&buffer->mutex, NULL);
pthread_cond_init(&buffer->empty, NULL);
pthread_cond_init(&buffer->full, NULL);
*rbuf = buffer;
return ISO_SUCCESS;
}
/**
* Write count bytes into buffer. It blocks until all bytes where written or
* reader close the buffer.
*
* @param buf
* the buffer
* @param data
* pointer to a memory region of at least coun bytes, from which data
* will be read.
* @param
* Number of bytes to write
* @return
* 1 succes, 0 read finished, < 0 error
*/
int iso_ring_buffer_write(IsoRingBuffer *buf, uint8_t *data, size_t count)
{
size_t len;
int bytes_write = 0;
if (buf == NULL || data == NULL) {
return ISO_NULL_POINTER;
}
while (bytes_write < count) {
pthread_mutex_lock(&buf->mutex);
while (buf->size == BUFFER_CAPACITY) {
/*
* Note. There's only a writer, so we have no race conditions.
* Thus, the while(buf->size == BUFFER_CAPACITY) is used here
* only to propertly detect the reader has been cancelled
*/
if (buf->rend) {
/* the read procces has been finished */
pthread_mutex_unlock(&buf->mutex);
return 0;
}
buf->times_full++;
/* wait until space available */
pthread_cond_wait(&buf->full, &buf->mutex);
}
len = MIN(count - bytes_write, BUFFER_CAPACITY - buf->size);
if (buf->wpos + len > BUFFER_CAPACITY) {
len = BUFFER_CAPACITY - buf->wpos;
}
memcpy(buf->buf + buf->wpos, data + bytes_write, len);
buf->wpos = (buf->wpos + len) % (BUFFER_CAPACITY);
bytes_write += len;
buf->size += len;
/* wake up reader */
pthread_cond_signal(&buf->empty);
pthread_mutex_unlock(&buf->mutex);
}
return ISO_SUCCESS;
}
/**
* Read count bytes from the buffer into dest. It blocks until the desired
* bytes has been read. If the writer finishes before outputting enought
* bytes, 0 (EOF) is returned, the number of bytes already read remains
* unknown.
*
* @return
* 1 success, 0 EOF, < 0 error
*/
int iso_ring_buffer_read(IsoRingBuffer *buf, uint8_t *dest, size_t count)
{
size_t len;
int bytes_read = 0;
if (buf == NULL || dest == NULL) {
return ISO_NULL_POINTER;
}
while (bytes_read < count) {
pthread_mutex_lock(&buf->mutex);
while (buf->size == 0) {
/*
* Note. There's only a reader, so we have no race conditions.
* Thus, the while(buf->size == 0) is used here just to ensure
* a reader detects the EOF propertly if the writer has been
* canceled while the reader was waiting
*/
if (buf->wend) {
/* the writer procces has been finished */
pthread_mutex_unlock(&buf->mutex);
return 0; /* EOF */
}
buf->times_empty++;
/* wait until data available */
pthread_cond_wait(&buf->empty, &buf->mutex);
}
len = MIN(count - bytes_read, buf->size);
if (buf->rpos + len > BUFFER_CAPACITY) {
len = BUFFER_CAPACITY - buf->rpos;
}
memcpy(dest + bytes_read, buf->buf + buf->rpos, len);
buf->rpos = (buf->rpos + len) % (BUFFER_CAPACITY);
bytes_read += len;
buf->size -= len;
/* wake up the writer */
pthread_cond_signal(&buf->full);
pthread_mutex_unlock(&buf->mutex);
}
return ISO_SUCCESS;
}
void iso_ring_buffer_writer_close(IsoRingBuffer *buf)
{
pthread_mutex_lock(&buf->mutex);
buf->wend = 1;
/* ensure no reader is waiting */
pthread_cond_signal(&buf->empty);
pthread_mutex_unlock(&buf->mutex);
}
void iso_ring_buffer_reader_close(IsoRingBuffer *buf)
{
pthread_mutex_lock(&buf->mutex);
buf->rend = 1;
/* ensure no writer is waiting */
pthread_cond_signal(&buf->full);
pthread_mutex_unlock(&buf->mutex);
}
/**
* Get the times the buffer was full.
*/
unsigned int iso_ring_buffer_get_times_full(IsoRingBuffer *buf)
{
return buf->times_full;
}
/**
* Get the times the buffer was empty.
*/
unsigned int iso_ring_buffer_get_times_empty(IsoRingBuffer *buf)
{
return buf->times_empty;
}

82
src/buffer.h Normal file
View File

@ -0,0 +1,82 @@
/*
* Copyright (c) 2007 Vreixo Formoso
*
* This file is part of the libisofs project; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation. See COPYING file for details.
*/
#ifndef LIBISO_BUFFER_H_
#define LIBISO_BUFFER_H_
#include <stdlib.h>
#include <stdint.h>
/* 2 MB buffer */
#define BLOCK_SIZE 2048
#define BUFFER_SIZE 1024
typedef struct iso_ring_buffer IsoRingBuffer;
/**
* Create a new buffer.
*
* The created buffer can be freed with free(3)
*
* @return
* 1 success, < 0 error
*/
int iso_ring_buffer_new(IsoRingBuffer **rbuf);
/**
* Write count bytes into buffer. It blocks until all bytes where written or
* reader close the buffer.
*
* @param buf
* the buffer
* @param data
* pointer to a memory region of at least coun bytes, from which data
* will be read.
* @param
* Number of bytes to write
* @return
* 1 succes, 0 read finished, < 0 error
*/
int iso_ring_buffer_write(IsoRingBuffer *buf, uint8_t *data, size_t count);
/**
* Read count bytes from the buffer into dest. It blocks until the desired
* bytes has been read. If the writer finishes before outputting enought
* bytes, 0 (EOF) is returned, the number of bytes already read remains
* unknown.
*
* @return
* 1 success, 0 EOF, < 0 error
*/
int iso_ring_buffer_read(IsoRingBuffer *buf, uint8_t *dest, size_t count);
/**
* Close the buffer (to be called by the writer).
* You have to explicity close the buffer when you don't have more data to
* write, otherwise reader will be waiting forever.
*/
void iso_ring_buffer_writer_close(IsoRingBuffer *buf);
/**
* Close the buffer (to be called by the reader).
* If for any reason you don't want to read more data, you need to call this
* to let the writer thread finish.
*/
void iso_ring_buffer_reader_close(IsoRingBuffer *buf);
/**
* Get the times the buffer was full.
*/
unsigned int iso_ring_buffer_get_times_full(IsoRingBuffer *buf);
/**
* Get the times the buffer was empty.
*/
unsigned int iso_ring_buffer_get_times_empty(IsoRingBuffer *buf);
#endif /*LIBISO_BUFFER_H_*/

4
src/ecma119.c
View File

@ -705,8 +705,8 @@ int ecma119_image_new(IsoImage *src, Ecma119WriteOpts *opts,
pthread_attr_init(&(target->th_attr));
pthread_attr_setdetachstate(&(target->th_attr), PTHREAD_CREATE_JOINABLE);
ret = pthread_create(&(target->wthread), NULL, write_function,
(void *) target);
ret = pthread_create(&(target->wthread), &(target->th_attr),
write_function, (void *) target);
if (ret != 0) {
iso_msg_fatal(target->image, LIBISO_THREAD_ERROR,
"Cannot create writer thread");