xapian-applications/omega/worker_comms.cc

   1 /** @file
   2  * @brief Communication with worker processes
   3  */
   4 /* Copyright (C) 2011,2022,2023 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation; either version 2 of the
   9  * License, or (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, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301
  19  * USA
  20  */
  21
  22 #include <config.h>
  23
  24 #include "worker_comms.h"
  25
  26 using namespace std;
  27
  28 const int buffer_size = 4096;
  29
  30 bool
  31 read_string(FILE* f, string& s)
  32 {
  33     // Extracting the length of the string
  34     int ch = getc(f);
  35     if (ch < 0) return false;
  36     size_t len = ch;
  37     if (len >= 253) {
  38         unsigned i = len - 251;
  39         len = 0;
  40         for ( ; i; --i) {
  41             ch = getc(f);
  42             if (ch < 0) return false;
  43             len = (len << 8) | ch;
  44         }
  45     }
  46
  47     s.resize(0);
  48     s.reserve(len);
  49
  50     // Reading the string
  51     char buf[buffer_size];
  52
  53     while (len) {
  54         size_t n = fread(buf, 1, min(sizeof(buf), len), f);
  55         if (n == 0) {
  56             // Error or EOF!
  57             return false;
  58         }
  59         s.append(buf, size_t(n));
  60         len -= n;
  61     }
  62
  63     return true;
  64 }
  65
  66 bool
  67 write_string(FILE* f, const char* p, size_t len)
  68 {
  69     if (len < 253) {
  70         putc(static_cast<unsigned char>(len), f);
  71     } else if (len < 0x10000) {
  72         putc(253, f);
  73         putc(static_cast<unsigned char>(len >> 8), f);
  74         putc(static_cast<unsigned char>(len), f);
  75     } else if (len < 0x1000000) {
  76         putc(254, f);
  77         putc(static_cast<unsigned char>(len >> 16), f);
  78         putc(static_cast<unsigned char>(len >> 8), f);
  79         putc(static_cast<unsigned char>(len), f);
  80     } else {
  81         putc(255, f);
  82         putc(static_cast<unsigned char>(len >> 24), f);
  83         putc(static_cast<unsigned char>(len >> 16), f);
  84         putc(static_cast<unsigned char>(len >> 8), f);
  85         putc(static_cast<unsigned char>(len), f);
  86     }
  87
  88     while (len) {
  89         size_t n = fwrite(p, 1, len, f);
  90         if (n == 0) {
  91             // EOF.
  92             return false;
  93         }
  94         p += n;
  95         len -= n;
  96     }
  97
  98     return true;
  99 }
 100
 101 bool
 102 read_unsigned(FILE* f, unsigned& v)
 103 {
 104     unsigned char data[(sizeof(v) * 8 + 6) / 7];
 105     unsigned char* p = data;
 106     int ch;
 107     do {
 108         ch = getc(f);
 109         if (p - data == sizeof(data) || ch < 0) return false;
 110         *p++ = ch & 0x7f;
 111     } while (ch & 0x80);
 112     v = 0;
 113     do {
 114         --p;
 115         v = (v << 7) | *p;
 116     } while (p > data);
 117     return true;
 118 }
 119
 120 bool
 121 read_unsigned(FILE* f, unsigned long& v)
 122 {
 123     unsigned char data[(sizeof(v) * 8 + 6) / 7];
 124     unsigned char* p = data;
 125     int ch;
 126     do {
 127         ch = getc(f);
 128         if (p - data == sizeof(data) || ch < 0) return false;
 129         *p++ = ch & 0x7f;
 130     } while (ch & 0x80);
 131     v = 0;
 132     do {
 133         --p;
 134         v = (v << 7) | *p;
 135     } while (p > data);
 136     return true;
 137 }
 138
 139 bool
 140 write_unsigned(FILE* f, unsigned long v)
 141 {
 142     while (v >= 0x80) {
 143         if (putc(v | 0x80, f) < 0) return false;
 144         v >>= 7;
 145     }
 146     return !(putc(v, f) < 0);
 147 }
 148
 149 bool
 150 write_unsigned(FILE* f, unsigned v)
 151 {
 152     while (v >= 0x80) {
 153         if (putc(v | 0x80, f) < 0) return false;
 154         v >>= 7;
 155     }
 156     return !(putc(v, f) < 0);
 157 }