pkt-line: allow peeking a packet line without consuming it
[git/git.git] / 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_write_fmt(int fd, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
24 void packet_buf_flush(struct strbuf *buf);
25 void packet_write(int fd_out, const char *buf, size_t size);
26 void packet_buf_write(struct strbuf *buf, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
27 int packet_flush_gently(int fd);
28 int packet_write_fmt_gently(int fd, const char *fmt, ...) __attribute__((format (printf, 2, 3)));
29 int write_packetized_from_fd(int fd_in, int fd_out);
30 int write_packetized_from_buf(const char *src_in, size_t len, int fd_out);
31
32 /*
33 * Read a packetized line into the buffer, which must be at least size bytes
34 * long. The return value specifies the number of bytes read into the buffer.
35 *
36 * If src_buffer and *src_buffer are not NULL, it should point to a buffer
37 * containing the packet data to parse, of at least *src_len bytes. After the
38 * function returns, src_buf will be incremented and src_len decremented by the
39 * number of bytes consumed.
40 *
41 * If src_buffer (or *src_buffer) is NULL, then data is read from the
42 * descriptor "fd".
43 *
44 * If options does not contain PACKET_READ_GENTLE_ON_EOF, we will die under any
45 * of the following conditions:
46 *
47 * 1. Read error from descriptor.
48 *
49 * 2. Protocol error from the remote (e.g., bogus length characters).
50 *
51 * 3. Receiving a packet larger than "size" bytes.
52 *
53 * 4. Truncated output from the remote (e.g., we expected a packet but got
54 * EOF, or we got a partial packet followed by EOF).
55 *
56 * If options does contain PACKET_READ_GENTLE_ON_EOF, we will not die on
57 * condition 4 (truncated input), but instead return -1. However, we will still
58 * die for the other 3 conditions.
59 *
60 * If options contains PACKET_READ_CHOMP_NEWLINE, a trailing newline (if
61 * present) is removed from the buffer before returning.
62 */
63 #define PACKET_READ_GENTLE_ON_EOF (1u<<0)
64 #define PACKET_READ_CHOMP_NEWLINE (1u<<1)
65 int packet_read(int fd, char **src_buffer, size_t *src_len, char
66 *buffer, unsigned size, int options);
67
68 /*
69 * Read a packetized line into a buffer like the 'packet_read()' function but
70 * returns an 'enum packet_read_status' which indicates the status of the read.
71 * The number of bytes read will be assigined to *pktlen if the status of the
72 * read was 'PACKET_READ_NORMAL'.
73 */
74 enum packet_read_status {
75 PACKET_READ_EOF,
76 PACKET_READ_NORMAL,
77 PACKET_READ_FLUSH,
78 };
79 enum packet_read_status packet_read_with_status(int fd, char **src_buffer,
80 size_t *src_len, char *buffer,
81 unsigned size, int *pktlen,
82 int options);
83
84 /*
85 * Convenience wrapper for packet_read that is not gentle, and sets the
86 * CHOMP_NEWLINE option. The return value is NULL for a flush packet,
87 * and otherwise points to a static buffer (that may be overwritten by
88 * subsequent calls). If the size parameter is not NULL, the length of the
89 * packet is written to it.
90 */
91 char *packet_read_line(int fd, int *size);
92
93 /*
94 * Convenience wrapper for packet_read that sets the PACKET_READ_GENTLE_ON_EOF
95 * and CHOMP_NEWLINE options. The return value specifies the number of bytes
96 * read into the buffer or -1 on truncated input. If the *dst_line parameter
97 * is not NULL it will return NULL for a flush packet or when the number of
98 * bytes copied is zero and otherwise points to a static buffer (that may be
99 * overwritten by subsequent calls). If the size parameter is not NULL, the
100 * length of the packet is written to it.
101 */
102 int packet_read_line_gently(int fd, int *size, char **dst_line);
103
104 /*
105 * Same as packet_read_line, but read from a buf rather than a descriptor;
106 * see packet_read for details on how src_* is used.
107 */
108 char *packet_read_line_buf(char **src_buf, size_t *src_len, int *size);
109
110 /*
111 * Reads a stream of variable sized packets until a flush packet is detected.
112 */
113 ssize_t read_packetized_to_strbuf(int fd_in, struct strbuf *sb_out);
114
115 struct packet_reader {
116 /* source file descriptor */
117 int fd;
118
119 /* source buffer and its size */
120 char *src_buffer;
121 size_t src_len;
122
123 /* buffer that pkt-lines are read into and its size */
124 char *buffer;
125 unsigned buffer_size;
126
127 /* options to be used during reads */
128 int options;
129
130 /* status of the last read */
131 enum packet_read_status status;
132
133 /* length of data read during the last read */
134 int pktlen;
135
136 /* the last line read */
137 const char *line;
138
139 /* indicates if a line has been peeked */
140 int line_peeked;
141 };
142
143 /*
144 * Initialize a 'struct packet_reader' object which is an
145 * abstraction around the 'packet_read_with_status()' function.
146 */
147 extern void packet_reader_init(struct packet_reader *reader, int fd,
148 char *src_buffer, size_t src_len,
149 int options);
150
151 /*
152 * Perform a packet read and return the status of the read.
153 * The values of 'pktlen' and 'line' are updated based on the status of the
154 * read as follows:
155 *
156 * PACKET_READ_ERROR: 'pktlen' is set to '-1' and 'line' is set to NULL
157 * PACKET_READ_NORMAL: 'pktlen' is set to the number of bytes read
158 * 'line' is set to point at the read line
159 * PACKET_READ_FLUSH: 'pktlen' is set to '0' and 'line' is set to NULL
160 */
161 extern enum packet_read_status packet_reader_read(struct packet_reader *reader);
162
163 /*
164 * Peek the next packet line without consuming it and return the status.
165 * The next call to 'packet_reader_read()' will perform a read of the same line
166 * that was peeked, consuming the line.
167 *
168 * Peeking multiple times without calling 'packet_reader_read()' will return
169 * the same result.
170 */
171 extern enum packet_read_status packet_reader_peek(struct packet_reader *reader);
172
173 #define DEFAULT_PACKET_MAX 1000
174 #define LARGE_PACKET_MAX 65520
175 #define LARGE_PACKET_DATA_MAX (LARGE_PACKET_MAX - 4)
176 extern char packet_buffer[LARGE_PACKET_MAX];
177
178 #endif