pkt-line.c

   1 #include "cache.h"
   2 #include "pkt-line.h"
   3
   4 static const char *packet_trace_prefix = "git";
   5 static const char trace_key[] = "GIT_TRACE_PACKET";
   6
   7 void packet_trace_identity(const char *prog)
   8 {
   9         packet_trace_prefix = xstrdup(prog);
  10 }
  11
  12 static void packet_trace(const char *buf, unsigned int len, int write)
  13 {
  14         int i;
  15         struct strbuf out;
  16
  17         if (!trace_want(trace_key))
  18                 return;
  19
  20         /* +32 is just a guess for header + quoting */
  21         strbuf_init(&out, len+32);
  22
  23         strbuf_addf(&out, "packet: %12s%c ",
  24                     packet_trace_prefix, write ? '>' : '<');
  25
  26         if ((len >= 4 && !prefixcmp(buf, "PACK")) ||
  27             (len >= 5 && !prefixcmp(buf+1, "PACK"))) {
  28                 strbuf_addstr(&out, "PACK ...");
  29                 unsetenv(trace_key);
  30         }
  31         else {
  32                 /* XXX we should really handle printable utf8 */
  33                 for (i = 0; i < len; i++) {
  34                         /* suppress newlines */
  35                         if (buf[i] == '\n')
  36                                 continue;
  37                         if (buf[i] >= 0x20 && buf[i] <= 0x7e)
  38                                 strbuf_addch(&out, buf[i]);
  39                         else
  40                                 strbuf_addf(&out, "\\%o", buf[i]);
  41                 }
  42         }
  43
  44         strbuf_addch(&out, '\n');
  45         trace_strbuf(trace_key, &out);
  46         strbuf_release(&out);
  47 }
  48
  49 /*
  50  * Write a packetized stream, where each line is preceded by
  51  * its length (including the header) as a 4-byte hex number.
  52  * A length of 'zero' means end of stream (and a length of 1-3
  53  * would be an error).
  54  *
  55  * This is all pretty stupid, but we use this packetized line
  56  * format to make a streaming format possible without ever
  57  * over-running the read buffers. That way we'll never read
  58  * into what might be the pack data (which should go to another
  59  * process entirely).
  60  *
  61  * The writing side could use stdio, but since the reading
  62  * side can't, we stay with pure read/write interfaces.
  63  */
  64 ssize_t safe_write(int fd, const void *buf, ssize_t n)
  65 {
  66         ssize_t nn = n;
  67         while (n) {
  68                 int ret = xwrite(fd, buf, n);
  69                 if (ret > 0) {
  70                         buf = (char *) buf + ret;
  71                         n -= ret;
  72                         continue;
  73                 }
  74                 if (!ret)
  75                         die("write error (disk full?)");
  76                 die_errno("write error");
  77         }
  78         return nn;
  79 }
  80
  81 /*
  82  * If we buffered things up above (we don't, but we should),
  83  * we'd flush it here
  84  */
  85 void packet_flush(int fd)
  86 {
  87         packet_trace("0000", 4, 1);
  88         safe_write(fd, "0000", 4);
  89 }
  90
  91 void packet_buf_flush(struct strbuf *buf)
  92 {
  93         packet_trace("0000", 4, 1);
  94         strbuf_add(buf, "0000", 4);
  95 }
  96
  97 #define hex(a) (hexchar[(a) & 15])
  98 static char buffer[1000];
  99 static unsigned format_packet(const char *fmt, va_list args)
 100 {
 101         static char hexchar[] = "0123456789abcdef";
 102         unsigned n;
 103
 104         n = vsnprintf(buffer + 4, sizeof(buffer) - 4, fmt, args);
 105         if (n >= sizeof(buffer)-4)
 106                 die("protocol error: impossibly long line");
 107         n += 4;
 108         buffer[0] = hex(n >> 12);
 109         buffer[1] = hex(n >> 8);
 110         buffer[2] = hex(n >> 4);
 111         buffer[3] = hex(n);
 112         packet_trace(buffer+4, n-4, 1);
 113         return n;
 114 }
 115
 116 void packet_write(int fd, const char *fmt, ...)
 117 {
 118         va_list args;
 119         unsigned n;
 120
 121         va_start(args, fmt);
 122         n = format_packet(fmt, args);
 123         va_end(args);
 124         safe_write(fd, buffer, n);
 125 }
 126
 127 void packet_buf_write(struct strbuf *buf, const char *fmt, ...)
 128 {
 129         va_list args;
 130         unsigned n;
 131
 132         va_start(args, fmt);
 133         n = format_packet(fmt, args);
 134         va_end(args);
 135         strbuf_add(buf, buffer, n);
 136 }
 137
 138 static int safe_read(int fd, void *buffer, unsigned size, int return_line_fail)
 139 {
 140         ssize_t ret = read_in_full(fd, buffer, size);
 141         if (ret < 0)
 142                 die_errno("read error");
 143         else if (ret < size) {
 144                 if (return_line_fail)
 145                         return -1;
 146
 147                 die("The remote end hung up unexpectedly");
 148         }
 149
 150         return ret;
 151 }
 152
 153 static int packet_length(const char *linelen)
 154 {
 155         int n;
 156         int len = 0;
 157
 158         for (n = 0; n < 4; n++) {
 159                 unsigned char c = linelen[n];
 160                 len <<= 4;
 161                 if (c >= '0' && c <= '9') {
 162                         len += c - '0';
 163                         continue;
 164                 }
 165                 if (c >= 'a' && c <= 'f') {
 166                         len += c - 'a' + 10;
 167                         continue;
 168                 }
 169                 if (c >= 'A' && c <= 'F') {
 170                         len += c - 'A' + 10;
 171                         continue;
 172                 }
 173                 return -1;
 174         }
 175         return len;
 176 }
 177
 178 static int packet_read_internal(int fd, char *buffer, unsigned size, int return_line_fail)
 179 {
 180         int len, ret;
 181         char linelen[4];
 182
 183         ret = safe_read(fd, linelen, 4, return_line_fail);
 184         if (return_line_fail && ret < 0)
 185                 return ret;
 186         len = packet_length(linelen);
 187         if (len < 0)
 188                 die("protocol error: bad line length character: %.4s", linelen);
 189         if (!len) {
 190                 packet_trace("0000", 4, 0);
 191                 return 0;
 192         }
 193         len -= 4;
 194         if (len >= size)
 195                 die("protocol error: bad line length %d", len);
 196         ret = safe_read(fd, buffer, len, return_line_fail);
 197         if (return_line_fail && ret < 0)
 198                 return ret;
 199         buffer[len] = 0;
 200         packet_trace(buffer, len, 0);
 201         return len;
 202 }
 203
 204 int packet_read(int fd, char *buffer, unsigned size)
 205 {
 206         return packet_read_internal(fd, buffer, size, 1);
 207 }
 208
 209 int packet_read_line(int fd, char *buffer, unsigned size)
 210 {
 211         return packet_read_internal(fd, buffer, size, 0);
 212 }
 213
 214 int packet_get_line(struct strbuf *out,
 215         char **src_buf, size_t *src_len)
 216 {
 217         int len;
 218
 219         if (*src_len < 4)
 220                 return -1;
 221         len = packet_length(*src_buf);
 222         if (len < 0)
 223                 return -1;
 224         if (!len) {
 225                 *src_buf += 4;
 226                 *src_len -= 4;
 227                 packet_trace("0000", 4, 0);
 228                 return 0;
 229         }
 230         if (*src_len < len)
 231                 return -2;
 232
 233         *src_buf += 4;
 234         *src_len -= 4;
 235         len -= 4;
 236
 237         strbuf_add(out, *src_buf, len);
 238         *src_buf += len;
 239         *src_len -= len;
 240         packet_trace(out->buf, out->len, 0);
 241         return len;
 242 }