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tag: v1.6.0
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Octocat-spinner-32-eaf2f5

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file 110 lines (101 sloc) 2.472 kb
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#include "cache.h"
#include "pkt-line.h"

/*
* Write a packetized stream, where each line is preceded by
* its length (including the header) as a 4-byte hex number.
* A length of 'zero' means end of stream (and a length of 1-3
* would be an error).
*
* This is all pretty stupid, but we use this packetized line
* format to make a streaming format possible without ever
* over-running the read buffers. That way we'll never read
* into what might be the pack data (which should go to another
* process entirely).
*
* The writing side could use stdio, but since the reading
* side can't, we stay with pure read/write interfaces.
*/
ssize_t safe_write(int fd, const void *buf, ssize_t n)
{
ssize_t nn = n;
while (n) {
int ret = xwrite(fd, buf, n);
if (ret > 0) {
buf = (char *) buf + ret;
n -= ret;
continue;
}
if (!ret)
die("write error (disk full?)");
die("write error (%s)", strerror(errno));
}
return nn;
}

/*
* If we buffered things up above (we don't, but we should),
* we'd flush it here
*/
void packet_flush(int fd)
{
safe_write(fd, "0000", 4);
}

#define hex(a) (hexchar[(a) & 15])
void packet_write(int fd, const char *fmt, ...)
{
static char buffer[1000];
static char hexchar[] = "0123456789abcdef";
va_list args;
unsigned n;

va_start(args, fmt);
n = vsnprintf(buffer + 4, sizeof(buffer) - 4, fmt, args);
va_end(args);
if (n >= sizeof(buffer)-4)
die("protocol error: impossibly long line");
n += 4;
buffer[0] = hex(n >> 12);
buffer[1] = hex(n >> 8);
buffer[2] = hex(n >> 4);
buffer[3] = hex(n);
safe_write(fd, buffer, n);
}

static void safe_read(int fd, void *buffer, unsigned size)
{
ssize_t ret = read_in_full(fd, buffer, size);
if (ret < 0)
die("read error (%s)", strerror(errno));
else if (ret < size)
die("The remote end hung up unexpectedly");
}

int packet_read_line(int fd, char *buffer, unsigned size)
{
int n;
unsigned len;
char linelen[4];

safe_read(fd, linelen, 4);

len = 0;
for (n = 0; n < 4; n++) {
unsigned char c = linelen[n];
len <<= 4;
if (c >= '0' && c <= '9') {
len += c - '0';
continue;
}
if (c >= 'a' && c <= 'f') {
len += c - 'a' + 10;
continue;
}
if (c >= 'A' && c <= 'F') {
len += c - 'A' + 10;
continue;
}
die("protocol error: bad line length character");
}
if (!len)
return 0;
len -= 4;
if (len >= size)
die("protocol error: bad line length %d", len);
safe_read(fd, buffer, len);
buffer[len] = 0;
return len;
}
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