tools/lib/traceevent/trace-seq.c

   1 /*
   2  * Copyright (C) 2009 Red Hat Inc, Steven Rostedt <srostedt@redhat.com>
   3  *
   4  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   5  * This program is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation;
   8  * version 2.1 of the License (not later!)
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this program; if not,  see <http://www.gnu.org/licenses>
  17  *
  18  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  19  */
  20 #include <stdio.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <stdarg.h>
  24
  25 #include "event-parse.h"
  26 #include "event-utils.h"
  27
  28 /*
  29  * The TRACE_SEQ_POISON is to catch the use of using
  30  * a trace_seq structure after it was destroyed.
  31  */
  32 #define TRACE_SEQ_POISON        ((void *)0xdeadbeef)
  33 #define TRACE_SEQ_CHECK(s)                                              \
  34 do {                                                                    \
  35         if ((s)->buffer == TRACE_SEQ_POISON)                    \
  36                 die("Usage of trace_seq after it was destroyed");       \
  37 } while (0)
  38
  39 /**
  40  * trace_seq_init - initialize the trace_seq structure
  41  * @s: a pointer to the trace_seq structure to initialize
  42  */
  43 void trace_seq_init(struct trace_seq *s)
  44 {
  45         s->len = 0;
  46         s->readpos = 0;
  47         s->buffer_size = TRACE_SEQ_BUF_SIZE;
  48         s->buffer = malloc_or_die(s->buffer_size);
  49 }
  50
  51 /**
  52  * trace_seq_reset - re-initialize the trace_seq structure
  53  * @s: a pointer to the trace_seq structure to reset
  54  */
  55 void trace_seq_reset(struct trace_seq *s)
  56 {
  57         if (!s)
  58                 return;
  59         TRACE_SEQ_CHECK(s);
  60         s->len = 0;
  61         s->readpos = 0;
  62 }
  63
  64 /**
  65  * trace_seq_destroy - free up memory of a trace_seq
  66  * @s: a pointer to the trace_seq to free the buffer
  67  *
  68  * Only frees the buffer, not the trace_seq struct itself.
  69  */
  70 void trace_seq_destroy(struct trace_seq *s)
  71 {
  72         if (!s)
  73                 return;
  74         TRACE_SEQ_CHECK(s);
  75         free(s->buffer);
  76         s->buffer = TRACE_SEQ_POISON;
  77 }
  78
  79 static void expand_buffer(struct trace_seq *s)
  80 {
  81         s->buffer_size += TRACE_SEQ_BUF_SIZE;
  82         s->buffer = realloc(s->buffer, s->buffer_size);
  83         if (!s->buffer)
  84                 die("Can't allocate trace_seq buffer memory");
  85 }
  86
  87 /**
  88  * trace_seq_printf - sequence printing of trace information
  89  * @s: trace sequence descriptor
  90  * @fmt: printf format string
  91  *
  92  * It returns 0 if the trace oversizes the buffer's free
  93  * space, 1 otherwise.
  94  *
  95  * The tracer may use either sequence operations or its own
  96  * copy to user routines. To simplify formating of a trace
  97  * trace_seq_printf is used to store strings into a special
  98  * buffer (@s). Then the output may be either used by
  99  * the sequencer or pulled into another buffer.
 100  */
 101 int
 102 trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
 103 {
 104         va_list ap;
 105         int len;
 106         int ret;
 107
 108         TRACE_SEQ_CHECK(s);
 109
 110  try_again:
 111         len = (s->buffer_size - 1) - s->len;
 112
 113         va_start(ap, fmt);
 114         ret = vsnprintf(s->buffer + s->len, len, fmt, ap);
 115         va_end(ap);
 116
 117         if (ret >= len) {
 118                 expand_buffer(s);
 119                 goto try_again;
 120         }
 121
 122         s->len += ret;
 123
 124         return 1;
 125 }
 126
 127 /**
 128  * trace_seq_vprintf - sequence printing of trace information
 129  * @s: trace sequence descriptor
 130  * @fmt: printf format string
 131  *
 132  * The tracer may use either sequence operations or its own
 133  * copy to user routines. To simplify formating of a trace
 134  * trace_seq_printf is used to store strings into a special
 135  * buffer (@s). Then the output may be either used by
 136  * the sequencer or pulled into another buffer.
 137  */
 138 int
 139 trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
 140 {
 141         int len;
 142         int ret;
 143
 144         TRACE_SEQ_CHECK(s);
 145
 146  try_again:
 147         len = (s->buffer_size - 1) - s->len;
 148
 149         ret = vsnprintf(s->buffer + s->len, len, fmt, args);
 150
 151         if (ret >= len) {
 152                 expand_buffer(s);
 153                 goto try_again;
 154         }
 155
 156         s->len += ret;
 157
 158         return len;
 159 }
 160
 161 /**
 162  * trace_seq_puts - trace sequence printing of simple string
 163  * @s: trace sequence descriptor
 164  * @str: simple string to record
 165  *
 166  * The tracer may use either the sequence operations or its own
 167  * copy to user routines. This function records a simple string
 168  * into a special buffer (@s) for later retrieval by a sequencer
 169  * or other mechanism.
 170  */
 171 int trace_seq_puts(struct trace_seq *s, const char *str)
 172 {
 173         int len;
 174
 175         TRACE_SEQ_CHECK(s);
 176
 177         len = strlen(str);
 178
 179         while (len > ((s->buffer_size - 1) - s->len))
 180                 expand_buffer(s);
 181
 182         memcpy(s->buffer + s->len, str, len);
 183         s->len += len;
 184
 185         return len;
 186 }
 187
 188 int trace_seq_putc(struct trace_seq *s, unsigned char c)
 189 {
 190         TRACE_SEQ_CHECK(s);
 191
 192         while (s->len >= (s->buffer_size - 1))
 193                 expand_buffer(s);
 194
 195         s->buffer[s->len++] = c;
 196
 197         return 1;
 198 }
 199
 200 void trace_seq_terminate(struct trace_seq *s)
 201 {
 202         TRACE_SEQ_CHECK(s);
 203
 204         /* There's always one character left on the buffer */
 205         s->buffer[s->len] = 0;
 206 }
 207
 208 int trace_seq_do_printf(struct trace_seq *s)
 209 {
 210         TRACE_SEQ_CHECK(s);
 211         return printf("%.*s", s->len, s->buffer);
 212 }