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authorLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-30 03:50:15 (GMT)
committerLinus Torvalds <torvalds@ppc970.osdl.org>2005-06-30 03:50:15 (GMT)
commitf3a3214e83be2905c57eff5d9035d169cae4644e (patch)
treed883e338e32ba1b07e31df7b2b9da44157d23210 /pkt-line.c
parent61221472a5f8591f2d06d5e5c5aafb03271b8066 (diff)
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Make send/receive-pack be closer to doing something interesting
Diffstat (limited to 'pkt-line.c')
-rw-r--r--pkt-line.c117
1 files changed, 117 insertions, 0 deletions
diff --git a/pkt-line.c b/pkt-line.c
new file mode 100644
index 0000000..6947304
--- /dev/null
+++ b/pkt-line.c
@@ -0,0 +1,117 @@
+#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.
+ */
+static void safe_write(int fd, const void *buf, unsigned n)
+{
+ while (n) {
+ int ret = write(fd, buf, n);
+ if (ret > 0) {
+ buf += ret;
+ n -= ret;
+ continue;
+ }
+ if (!ret)
+ die("write error (disk full?)");
+ if (errno == EAGAIN || errno == EINTR)
+ continue;
+ die("write error (%s)", strerror(errno));
+ }
+}
+
+/*
+ * 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)
+{
+ int n = 0;
+
+ while (n < size) {
+ int ret = read(fd, buffer + n, size - n);
+ if (ret < 0) {
+ if (errno == EINTR || errno == EAGAIN)
+ continue;
+ die("read error (%s)", strerror(errno));
+ }
+ if (!ret)
+ die("unexpected EOF");
+ n += ret;
+ }
+}
+
+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;
+}