ctdb/common/line.c

   1 /*
   2    Line based I/O over fds
   3
   4    Copyright (C) Amitay Isaacs  2018
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include "replace.h"
  21
  22 #include <talloc.h>
  23
  24 #include "lib/util/sys_rw.h"
  25
  26 #include "common/line.h"
  27
  28 struct line_read_state {
  29         line_process_fn_t callback;
  30         void *private_data;
  31         char *buf;
  32         size_t hint, len, offset;
  33         int num_lines;
  34 };
  35
  36 static bool line_read_one(char *buf, size_t start, size_t len, size_t *pos)
  37 {
  38         size_t i;
  39
  40         for (i=start; i<len; i++) {
  41                 if (buf[i] == '\n' || buf[i] == '\0') {
  42                         *pos = i;
  43                         return true;
  44                 }
  45         }
  46
  47         return false;
  48 }
  49
  50 static int line_read_process(struct line_read_state *state)
  51 {
  52         size_t start = 0;
  53         size_t pos = 0;
  54
  55         while (1) {
  56                 int ret;
  57                 bool ok;
  58
  59                 ok = line_read_one(state->buf, start, state->offset, &pos);
  60                 if (! ok) {
  61                         break;
  62                 }
  63
  64                 state->buf[pos] = '\0';
  65                 state->num_lines += 1;
  66
  67                 ret = state->callback(state->buf + start, state->private_data);
  68                 if (ret != 0) {
  69                         return ret;
  70                 }
  71
  72                 start = pos+1;
  73         }
  74
  75         if (pos > 0) {
  76                 if (pos+1 < state->offset) {
  77                         memmove(state->buf,
  78                                 state->buf + pos+1,
  79                                 state->offset - (pos+1));
  80                 }
  81                 state->offset -= (pos+1);
  82         }
  83
  84         return 0;
  85 }
  86
  87 int line_read(int fd,
  88               size_t length,
  89               TALLOC_CTX *mem_ctx,
  90               line_process_fn_t callback,
  91               void *private_data,
  92               int *num_lines)
  93 {
  94         struct line_read_state state;
  95
  96         if (length < 32) {
  97                 length = 32;
  98         }
  99
 100         state = (struct line_read_state) {
 101                 .callback = callback,
 102                 .private_data = private_data,
 103                 .hint = length,
 104         };
 105
 106         while (1) {
 107                 ssize_t n;
 108                 int ret;
 109
 110                 if (state.offset == state.len) {
 111                         state.len += state.hint;
 112                         state.buf = talloc_realloc_size(mem_ctx,
 113                                                         state.buf,
 114                                                         state.len);
 115                         if (state.buf == NULL) {
 116                                 return ENOMEM;
 117                         }
 118                 }
 119
 120                 n = sys_read(fd,
 121                              state.buf + state.offset,
 122                              state.len - state.offset);
 123                 if (n < 0) {
 124                         return errno;
 125                 }
 126                 if (n == 0) {
 127                         break;
 128                 }
 129
 130                 state.offset += n;
 131
 132                 ret = line_read_process(&state);
 133                 if (ret != 0) {
 134                         if (num_lines != NULL) {
 135                                 *num_lines = state.num_lines;
 136                         }
 137                         return ret;
 138                 }
 139         }
 140
 141         if (num_lines != NULL) {
 142                 *num_lines = state.num_lines;
 143         }
 144         return 0;
 145 }