pkt-line.h

   1 #ifndef PKTLINE_H
   2 #define PKTLINE_H
   3
   4 #include "git-compat-util.h"
   5 #include "strbuf.h"
   6
   7 /*
   8  * Write a packetized stream, where each line is preceded by
   9  * its length (including the header) as a 4-byte hex number.
  10  * A length of 'zero' means end of stream (and a length of 1-3
  11  * would be an error).
  12  *
  13  * This is all pretty stupid, but we use this packetized line
  14  * format to make a streaming format possible without ever
  15  * over-running the read buffers. That way we'll never read
  16  * into what might be the pack data (which should go to another
  17  * process entirely).
  18  *
  19  * The writing side could use stdio, but since the reading
  20  * side can't, we stay with pure read/write interfaces.
  21  */
  22 void packet_flush(int fd);
  23 void packet_delim(int fd);
  24 void packet_write_fmt(int fd, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
  25 void packet_buf_flush(struct strbuf *buf);
  26 void packet_buf_delim(struct strbuf *buf);
  27 void packet_write(int fd_out, const char *buf, size_t size);
  28 void packet_buf_write(struct strbuf *buf, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
  29 void packet_buf_write_len(struct strbuf *buf, const char *data, size_t len);
  30 int packet_flush_gently(int fd);
  31 int packet_write_fmt_gently(int fd, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
  32 int write_packetized_from_fd(int fd_in, int fd_out);
  33 int write_packetized_from_buf(const char *src_in, size_t len, int fd_out);
  34
  35 /*
  36  * Read a packetized line into the buffer, which must be at least size bytes
  37  * long. The return value specifies the number of bytes read into the buffer.
  38  *
  39  * If src_buffer and *src_buffer are not NULL, it should point to a buffer
  40  * containing the packet data to parse, of at least *src_len bytes.  After the
  41  * function returns, src_buf will be incremented and src_len decremented by the
  42  * number of bytes consumed.
  43  *
  44  * If src_buffer (or *src_buffer) is NULL, then data is read from the
  45  * descriptor "fd".
  46  *
  47  * If options does not contain PACKET_READ_GENTLE_ON_EOF, we will die under any
  48  * of the following conditions:
  49  *
  50  *   1. Read error from descriptor.
  51  *
  52  *   2. Protocol error from the remote (e.g., bogus length characters).
  53  *
  54  *   3. Receiving a packet larger than "size" bytes.
  55  *
  56  *   4. Truncated output from the remote (e.g., we expected a packet but got
  57  *      EOF, or we got a partial packet followed by EOF).
  58  *
  59  * If options does contain PACKET_READ_GENTLE_ON_EOF, we will not die on
  60  * condition 4 (truncated input), but instead return -1. However, we will still
  61  * die for the other 3 conditions.
  62  *
  63  * If options contains PACKET_READ_CHOMP_NEWLINE, a trailing newline (if
  64  * present) is removed from the buffer before returning.
  65  *
  66  * If options contains PACKET_READ_DIE_ON_ERR_PACKET, it dies when it sees an
  67  * ERR packet.
  68  */
  69 #define PACKET_READ_GENTLE_ON_EOF     (1u<<0)
  70 #define PACKET_READ_CHOMP_NEWLINE     (1u<<1)
  71 #define PACKET_READ_DIE_ON_ERR_PACKET (1u<<2)
  72 int packet_read(int fd, char **src_buffer, size_t *src_len, char
  73                 *buffer, unsigned size, int options);
  74
  75 /*
  76  * Read a packetized line into a buffer like the 'packet_read()' function but
  77  * returns an 'enum packet_read_status' which indicates the status of the read.
  78  * The number of bytes read will be assigined to *pktlen if the status of the
  79  * read was 'PACKET_READ_NORMAL'.
  80  */
  81 enum packet_read_status {
  82         PACKET_READ_EOF,
  83         PACKET_READ_NORMAL,
  84         PACKET_READ_FLUSH,
  85         PACKET_READ_DELIM,
  86 };
  87 enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
  88                                                 size_t *src_len, char *buffer,
  89                                                 unsigned size, int *pktlen,
  90                                                 int options);
  91
  92 /*
  93  * Convenience wrapper for packet_read that is not gentle, and sets the
  94  * CHOMP_NEWLINE option. The return value is NULL for a flush packet,
  95  * and otherwise points to a static buffer (that may be overwritten by
  96  * subsequent calls). If the size parameter is not NULL, the length of the
  97  * packet is written to it.
  98  */
  99 char *packet_read_line(int fd, int *size);
 100
 101 /*
 102  * Convenience wrapper for packet_read that sets the PACKET_READ_GENTLE_ON_EOF
 103  * and CHOMP_NEWLINE options. The return value specifies the number of bytes
 104  * read into the buffer or -1 on truncated input. If the *dst_line parameter
 105  * is not NULL it will return NULL for a flush packet or when the number of
 106  * bytes copied is zero and otherwise points to a static buffer (that may be
 107  * overwritten by subsequent calls). If the size parameter is not NULL, the
 108  * length of the packet is written to it.
 109  */
 110 int packet_read_line_gently(int fd, int *size, char **dst_line);
 111
 112 /*
 113  * Same as packet_read_line, but read from a buf rather than a descriptor;
 114  * see packet_read for details on how src_* is used.
 115  */
 116 char *packet_read_line_buf(char **src_buf, size_t *src_len, int *size);
 117
 118 /*
 119  * Reads a stream of variable sized packets until a flush packet is detected.
 120  */
 121 ssize_t read_packetized_to_strbuf(int fd_in, struct strbuf *sb_out);
 122
 123 struct packet_reader {
 124         /* source file descriptor */
 125         int fd;
 126
 127         /* source buffer and its size */
 128         char *src_buffer;
 129         size_t src_len;
 130
 131         /* buffer that pkt-lines are read into and its size */
 132         char *buffer;
 133         unsigned buffer_size;
 134
 135         /* options to be used during reads */
 136         int options;
 137
 138         /* status of the last read */
 139         enum packet_read_status status;
 140
 141         /* length of data read during the last read */
 142         int pktlen;
 143
 144         /* the last line read */
 145         const char *line;
 146
 147         /* indicates if a line has been peeked */
 148         int line_peeked;
 149 };
 150
 151 /*
 152  * Initialize a 'struct packet_reader' object which is an
 153  * abstraction around the 'packet_read_with_status()' function.
 154  */
 155 extern void packet_reader_init(struct packet_reader *reader, int fd,
 156                                char *src_buffer, size_t src_len,
 157                                int options);
 158
 159 /*
 160  * Perform a packet read and return the status of the read.
 161  * The values of 'pktlen' and 'line' are updated based on the status of the
 162  * read as follows:
 163  *
 164  * PACKET_READ_ERROR: 'pktlen' is set to '-1' and 'line' is set to NULL
 165  * PACKET_READ_NORMAL: 'pktlen' is set to the number of bytes read
 166  *                     'line' is set to point at the read line
 167  * PACKET_READ_FLUSH: 'pktlen' is set to '0' and 'line' is set to NULL
 168  */
 169 extern enum packet_read_status packet_reader_read(struct packet_reader *reader);
 170
 171 /*
 172  * Peek the next packet line without consuming it and return the status.
 173  * The next call to 'packet_reader_read()' will perform a read of the same line
 174  * that was peeked, consuming the line.
 175  *
 176  * Peeking multiple times without calling 'packet_reader_read()' will return
 177  * the same result.
 178  */
 179 extern enum packet_read_status packet_reader_peek(struct packet_reader *reader);
 180
 181 #define DEFAULT_PACKET_MAX 1000
 182 #define LARGE_PACKET_MAX 65520
 183 #define LARGE_PACKET_DATA_MAX (LARGE_PACKET_MAX - 4)
 184 extern char packet_buffer[LARGE_PACKET_MAX];
 185
 186 struct packet_writer {
 187         int dest_fd;
 188 };
 189
 190 void packet_writer_init(struct packet_writer *writer, int dest_fd);
 191
 192 /* These functions die upon failure. */
 193 __attribute__((format (printf, 2, 3)))
 194 void packet_writer_write(struct packet_writer *writer, const char *fmt, ...);
 195 __attribute__((format (printf, 2, 3)))
 196 void packet_writer_error(struct packet_writer *writer, const char *fmt, ...);
 197 void packet_writer_delim(struct packet_writer *writer);
 198 void packet_writer_flush(struct packet_writer *writer);
 199
 200 #endif