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/* libs/cutils/record_stream.c
**
** Copyright 2006, The Android Open Source Project
**
** Licensed under the Apache License, Version 2.0 (the "License");
** you may not use this file except in compliance with the License.
** You may obtain a copy of the License at
**
** http://www.apache.org/licenses/LICENSE-2.0
**
** Unless required by applicable law or agreed to in writing, software
** distributed under the License is distributed on an "AS IS" BASIS,
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
** See the License for the specific language governing permissions and
** limitations under the License.
*/
#include <cutils/record_stream.h>
#include <stdlib.h>
#include <unistd.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <stdint.h>
#if defined(_WIN32)
#include <winsock2.h> /* for ntohl */
#else
#include <netinet/in.h>
#endif
#define HEADER_SIZE 4
struct RecordStream {
int fd;
size_t maxRecordLen;
unsigned char *buffer;
unsigned char *unconsumed;
unsigned char *read_end;
unsigned char *buffer_end;
};
extern RecordStream *record_stream_new(int fd, size_t maxRecordLen)
{
RecordStream *ret;
assert (maxRecordLen <= 0xffff);
ret = (RecordStream *)calloc(1, sizeof(RecordStream));
ret->fd = fd;
ret->maxRecordLen = maxRecordLen;
ret->buffer = (unsigned char *)malloc (maxRecordLen + HEADER_SIZE);
ret->unconsumed = ret->buffer;
ret->read_end = ret->buffer;
ret->buffer_end = ret->buffer + maxRecordLen + HEADER_SIZE;
return ret;
}
extern void record_stream_free(RecordStream *rs)
{
free(rs->buffer);
free(rs);
}
/* returns NULL; if there isn't a full record in the buffer */
static unsigned char * getEndOfRecord (unsigned char *p_begin,
unsigned char *p_end)
{
size_t len;
unsigned char * p_ret;
if (p_end < p_begin + HEADER_SIZE) {
return NULL;
}
//First four bytes are length
len = ntohl(*((uint32_t *)p_begin));
p_ret = p_begin + HEADER_SIZE + len;
if (p_end < p_ret) {
return NULL;
}
return p_ret;
}
static void *getNextRecord (RecordStream *p_rs, size_t *p_outRecordLen)
{
unsigned char *record_start, *record_end;
record_end = getEndOfRecord (p_rs->unconsumed, p_rs->read_end);
if (record_end != NULL) {
/* one full line in the buffer */
record_start = p_rs->unconsumed + HEADER_SIZE;
p_rs->unconsumed = record_end;
*p_outRecordLen = record_end - record_start;
return record_start;
}
return NULL;
}
/**
* Reads the next record from stream fd
* Records are prefixed by a 16-bit big endian length value
* Records may not be larger than maxRecordLen
*
* Doesn't guard against EINTR
*
* p_outRecord and p_outRecordLen may not be NULL
*
* Return 0 on success, -1 on fail
* Returns 0 with *p_outRecord set to NULL on end of stream
* Returns -1 / errno = EAGAIN if it needs to read again
*/
int record_stream_get_next (RecordStream *p_rs, void ** p_outRecord,
size_t *p_outRecordLen)
{
void *ret;
ssize_t countRead;
/* is there one record already in the buffer? */
ret = getNextRecord (p_rs, p_outRecordLen);
if (ret != NULL) {
*p_outRecord = ret;
return 0;
}
// if the buffer is full and we don't have a full record
if (p_rs->unconsumed == p_rs->buffer
&& p_rs->read_end == p_rs->buffer_end
) {
// this should never happen
//ALOGE("max record length exceeded\n");
assert (0);
errno = EFBIG;
return -1;
}
if (p_rs->unconsumed != p_rs->buffer) {
// move remainder to the beginning of the buffer
size_t toMove;
toMove = p_rs->read_end - p_rs->unconsumed;
if (toMove) {
memmove(p_rs->buffer, p_rs->unconsumed, toMove);
}
p_rs->read_end = p_rs->buffer + toMove;
p_rs->unconsumed = p_rs->buffer;
}
countRead = read (p_rs->fd, p_rs->read_end, p_rs->buffer_end - p_rs->read_end);
if (countRead <= 0) {
/* note: end-of-stream drops through here too */
*p_outRecord = NULL;
return countRead;
}
p_rs->read_end += countRead;
ret = getNextRecord (p_rs, p_outRecordLen);
if (ret == NULL) {
/* not enough of a buffer to for a whole command */
errno = EAGAIN;
return -1;
}
*p_outRecord = ret;
return 0;
}
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