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/* buf.c - by Alen Stojanov and David van Moolenbroek, taken from procfs */
#include "devman.h"
#include "proto.h"
#include <stdarg.h>
#include <assert.h>
static char *buf;
static size_t left, used;
static off_t skip;
/*===========================================================================*
* buf_init *
*===========================================================================*/
void buf_init(char *ptr, size_t len, off_t start)
{
/* Initialize the buffer for fresh use. The output is to be stored into
* 'ptr' which is BUF_SIZE bytes in size, since that is the size we
* requested. Due to the way vsnprintf works, we cannot use the last
* byte of this buffer. The first 'start' bytes of the produced output
* are to be skipped. After that, a total of 'len' bytes are requested.
*/
buf = ptr;
skip = start;
left = MIN(len, BUF_SIZE - 1);
used = 0;
}
/*===========================================================================*
* buf_printf *
*===========================================================================*/
void buf_printf(char *fmt, ...)
{
/* Add formatted text to the end of the buffer.
*/
va_list args;
ssize_t len, max;
if (left == 0)
return;
/* There is no way to estimate how much space the result will take, so
* we need to produce the string even when skipping part of the start.
* The null terminating character is not part of the result, so room
* must be given for it to be stored after completely filling up the
* requested part of the buffer.
*/
max = MIN(skip + left + 1, BUF_SIZE);
va_start(args, fmt);
len = vsnprintf(&buf[used], max, fmt, args);
va_end(args);
/* The snprintf family returns the number of bytes that would be stored
* if the buffer were large enough, excluding the null terminator.
*/
if (len >= BUF_SIZE)
len = BUF_SIZE - 1;
if (skip > 0) {
assert(used == 0);
if (skip >= len) {
skip -= len;
return;
}
memmove(buf, &buf[skip], len - skip);
len -= skip;
skip = 0;
}
assert(skip == 0);
assert(len >= 0);
assert((ssize_t) left >= 0);
if (len > (ssize_t) left)
len = left;
used += len;
left -= len;
}
/*===========================================================================*
* buf_append *
*===========================================================================*/
void buf_append(char *data, size_t len)
{
/* Add arbitrary data to the end of the buffer.
*/
if (left == 0)
return;
if (skip > 0) {
if (skip >= (ssize_t) len) {
skip -= len;
return;
}
data += skip;
len -= skip;
skip = 0;
}
if (len > left)
len = left;
memcpy(&buf[used], data, len);
used += len;
left -= len;
}
/*===========================================================================*
* buf_result *
*===========================================================================*/
ssize_t buf_result(void)
{
/* Return the resulting number of bytes produced, not counting the
* trailing null character in the buffer.
*/
return used;
}
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