gzip

Go to the documentation of this file.

// Copyright (C) 2010, Guy Barrand. All rights reserved.
// See the file tools.license for terms.
 
#ifndef tools_gzip
#define tools_gzip
 
#include "signature"
 
namespace tools {
namespace file {
 
inline bool is_gzip(const std::string& a_file,bool& a_is){
  unsigned char head[4];
 {unsigned int num = 4;
  if(!signature(a_file,head,num)) {a_is = false;return false;}
  if(num!=4) {a_is = false;return true;}}
  if(head[0]!=31) {a_is = false;return true;}
  if(head[1]!=139) {a_is = false;return true;}
  //if(head[2]!=8) {a_is = false;return true;}
  //if(head[3]!=8) {a_is = false;return true;}
  a_is = true;
  return true;
}
 
inline bool gzip_usize(const std::string& a_file,unsigned int& a_usz){
  bool is;
  if(!is_gzip(a_file,is)) {a_usz=0;return false;}
  if(!is) {a_usz=0;return false;}
  FILE* file = ::fopen(a_file.c_str(),"rb");
  if(!file) {a_usz=0;return false;}
  ::fseek(file,-4,SEEK_END);
  unsigned char buf[4];
  size_t n = ::fread(buf,1,4,file);
  ::fclose(file);
  if(n!=4) {a_usz=0;return false;}
  unsigned int b4 = buf[0];
  unsigned int b3 = buf[1];
  unsigned int b2 = buf[2];
  unsigned int b1 = buf[3];
  a_usz = (b1 << 24) | ((b2 << 16) + (b3 << 8) + b4);
  return true;
}
 
}}
 
#endif