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, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  20  */
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <stdarg.h>
  25
  26 #include "event-parse.h"
  27 #include "event-utils.h"
  28
  29 /*
  30  * The TRACE_SEQ_POISON is to catch the use of using
  31  * a trace_seq structure after it was destroyed.
  32  */
  33 #define TRACE_SEQ_POISON        ((void *)0xdeadbeef)
  34 #define TRACE_SEQ_CHECK(s)                                              \
  35 do {                                                                    \
  36         if ((s)->buffer == TRACE_SEQ_POISON)                    \
  37                 die("Usage of trace_seq after it was destroyed");       \
  38 } while (0)
  39
  40 /**
  41  * trace_seq_init - initialize the trace_seq structure
  42  * @s: a pointer to the trace_seq structure to initialize
  43  */
  44 void trace_seq_init(struct trace_seq *s)
  45 {
  46         s->len = 0;
  47         s->readpos = 0;
  48         s->buffer_size = TRACE_SEQ_BUF_SIZE;
  49         s->buffer = malloc_or_die(s->buffer_size);
  50 }
  51
  52 /**
  53  * trace_seq_destroy - free up memory of a trace_seq
  54  * @s: a pointer to the trace_seq to free the buffer
  55  *
  56  * Only frees the buffer, not the trace_seq struct itself.
  57  */
  58 void trace_seq_destroy(struct trace_seq *s)
  59 {
  60         if (!s)
  61                 return;
  62         TRACE_SEQ_CHECK(s);
  63         free(s->buffer);
  64         s->buffer = TRACE_SEQ_POISON;
  65 }
  66
  67 static void expand_buffer(struct trace_seq *s)
  68 {
  69         s->buffer_size += TRACE_SEQ_BUF_SIZE;
  70         s->buffer = realloc(s->buffer, s->buffer_size);
  71         if (!s->buffer)
  72                 die("Can't allocate trace_seq buffer memory");
  73 }
  74
  75 /**
  76  * trace_seq_printf - sequence printing of trace information
  77  * @s: trace sequence descriptor
  78  * @fmt: printf format string
  79  *
  80  * It returns 0 if the trace oversizes the buffer's free
  81  * space, 1 otherwise.
  82  *
  83  * The tracer may use either sequence operations or its own
  84  * copy to user routines. To simplify formating of a trace
  85  * trace_seq_printf is used to store strings into a special
  86  * buffer (@s). Then the output may be either used by
  87  * the sequencer or pulled into another buffer.
  88  */
  89 int
  90 trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
  91 {
  92         va_list ap;
  93         int len;
  94         int ret;
  95
  96         TRACE_SEQ_CHECK(s);
  97
  98  try_again:
  99         len = (s->buffer_size - 1) - s->len;
 100
 101         va_start(ap, fmt);
 102         ret = vsnprintf(s->buffer + s->len, len, fmt, ap);
 103         va_end(ap);
 104
 105         if (ret >= len) {
 106                 expand_buffer(s);
 107                 goto try_again;
 108         }
 109
 110         s->len += ret;
 111
 112         return 1;
 113 }
 114
 115 /**
 116  * trace_seq_vprintf - sequence printing of trace information
 117  * @s: trace sequence descriptor
 118  * @fmt: printf format string
 119  *
 120  * The tracer may use either sequence operations or its own
 121  * copy to user routines. To simplify formating of a trace
 122  * trace_seq_printf is used to store strings into a special
 123  * buffer (@s). Then the output may be either used by
 124  * the sequencer or pulled into another buffer.
 125  */
 126 int
 127 trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
 128 {
 129         int len;
 130         int ret;
 131
 132         TRACE_SEQ_CHECK(s);
 133
 134  try_again:
 135         len = (s->buffer_size - 1) - s->len;
 136
 137         ret = vsnprintf(s->buffer + s->len, len, fmt, args);
 138
 139         if (ret >= len) {
 140                 expand_buffer(s);
 141                 goto try_again;
 142         }
 143
 144         s->len += ret;
 145
 146         return len;
 147 }
 148
 149 /**
 150  * trace_seq_puts - trace sequence printing of simple string
 151  * @s: trace sequence descriptor
 152  * @str: simple string to record
 153  *
 154  * The tracer may use either the sequence operations or its own
 155  * copy to user routines. This function records a simple string
 156  * into a special buffer (@s) for later retrieval by a sequencer
 157  * or other mechanism.
 158  */
 159 int trace_seq_puts(struct trace_seq *s, const char *str)
 160 {
 161         int len;
 162
 163         TRACE_SEQ_CHECK(s);
 164
 165         len = strlen(str);
 166
 167         while (len > ((s->buffer_size - 1) - s->len))
 168                 expand_buffer(s);
 169
 170         memcpy(s->buffer + s->len, str, len);
 171         s->len += len;
 172
 173         return len;
 174 }
 175
 176 int trace_seq_putc(struct trace_seq *s, unsigned char c)
 177 {
 178         TRACE_SEQ_CHECK(s);
 179
 180         while (s->len >= (s->buffer_size - 1))
 181                 expand_buffer(s);
 182
 183         s->buffer[s->len++] = c;
 184
 185         return 1;
 186 }
 187
 188 void trace_seq_terminate(struct trace_seq *s)
 189 {
 190         TRACE_SEQ_CHECK(s);
 191
 192         /* There's always one character left on the buffer */
 193         s->buffer[s->len] = 0;
 194 }
 195
 196 int trace_seq_do_printf(struct trace_seq *s)
 197 {
 198         TRACE_SEQ_CHECK(s);
 199         return printf("%.*s", s->len, s->buffer);
 200 }