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114 lines
2.4 KiB
C
114 lines
2.4 KiB
C
#include "cache.h"
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#include "pkt-line.h"
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/*
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* Write a packetized stream, where each line is preceded by
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* its length (including the header) as a 4-byte hex number.
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* A length of 'zero' means end of stream (and a length of 1-3
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* would be an error).
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*
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* This is all pretty stupid, but we use this packetized line
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* format to make a streaming format possible without ever
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* over-running the read buffers. That way we'll never read
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* into what might be the pack data (which should go to another
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* process entirely).
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*
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* The writing side could use stdio, but since the reading
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* side can't, we stay with pure read/write interfaces.
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*/
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ssize_t safe_write(int fd, const void *buf, ssize_t n)
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{
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ssize_t nn = n;
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while (n) {
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int ret = xwrite(fd, buf, n);
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if (ret > 0) {
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buf = (char *) buf + ret;
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n -= ret;
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continue;
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}
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if (!ret)
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die("write error (disk full?)");
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die("write error (%s)", strerror(errno));
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}
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return nn;
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}
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/*
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* If we buffered things up above (we don't, but we should),
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* we'd flush it here
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*/
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void packet_flush(int fd)
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{
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safe_write(fd, "0000", 4);
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}
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#define hex(a) (hexchar[(a) & 15])
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void packet_write(int fd, const char *fmt, ...)
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{
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static char buffer[1000];
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static char hexchar[] = "0123456789abcdef";
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va_list args;
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unsigned n;
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va_start(args, fmt);
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n = vsnprintf(buffer + 4, sizeof(buffer) - 4, fmt, args);
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va_end(args);
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if (n >= sizeof(buffer)-4)
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die("protocol error: impossibly long line");
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n += 4;
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buffer[0] = hex(n >> 12);
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buffer[1] = hex(n >> 8);
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buffer[2] = hex(n >> 4);
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buffer[3] = hex(n);
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safe_write(fd, buffer, n);
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}
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static void safe_read(int fd, void *buffer, unsigned size)
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{
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int n = 0;
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while (n < size) {
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int ret = xread(fd, (char *) buffer + n, size - n);
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if (ret < 0)
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die("read error (%s)", strerror(errno));
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if (!ret)
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die("unexpected EOF");
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n += ret;
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}
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}
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int packet_read_line(int fd, char *buffer, unsigned size)
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{
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int n;
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unsigned len;
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char linelen[4];
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safe_read(fd, linelen, 4);
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len = 0;
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for (n = 0; n < 4; n++) {
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unsigned char c = linelen[n];
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len <<= 4;
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if (c >= '0' && c <= '9') {
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len += c - '0';
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continue;
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}
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if (c >= 'a' && c <= 'f') {
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len += c - 'a' + 10;
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continue;
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}
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if (c >= 'A' && c <= 'F') {
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len += c - 'A' + 10;
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continue;
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}
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die("protocol error: bad line length character");
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}
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if (!len)
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return 0;
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len -= 4;
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if (len >= size)
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die("protocol error: bad line length %d", len);
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safe_read(fd, buffer, len);
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buffer[len] = 0;
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return len;
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}
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