无符号字符比较

Question

我有附加代码的问题。我希望用偏移量（它们之间的字节量）替换一些分隔符。我只有1个字节，如果偏移量大于254，我想用255替换它。在这种情况下，下一个找到的偏移量不应该被替换。替换部分工作正常...无论如何我无法识别是否最后一个分隔符被替换为255最后一次，它被跳过或转换，我不知道为什么/我在做什么错误。也许任何人都可以给我任何线索。这里的代码和最后的输出。我用（**）标记了分隔符，不应该被替换。

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#include <arpa/inet.h> 
#include "zlib.h" 


unsigned char *process(unsigned char *data, unsigned long size) 
{ 
     int i; 
     unsigned char *lastdel = data+1; 
     for (i=2;i<size; i++) 
     { 
       // if((unsigned char)*lastdel >254)printf(" %c <#######-------\n", *lastdel); 
       //if(*lastdel == (unsigned char) 255)printf(" %c <#######-------\n", *lastdel); 
       //if (!memcmp(lastdel,(unsigned char) 255, 1)) 
       //printf(" %c <#######-------\n", *lastdel); 
       //if(*lastdel == (unsigned char) 255)printf(" %c <#######-------\n", *lastdel); 
       //if(data[i] !='\x03' && data[i] !='\x1D' && data[i] !='\x1E'&& data[i] !='\x1C')continue; 
       //if(*lastdel >(unsigned char) 254 )printf(" %c <#######-------\n", *lastdel); 
       if(*lastdel >(unsigned char) 254 )printf(" %c <++++~~~++++++++#######-------\n", *lastdel); 
       if(data[i] =='\x03') 
       { 
         *lastdel = (&data[i] - lastdel-1 >255) ?(unsigned char) 255 : &data[i] - lastdel-1; 
         i+=2; 
         lastdel = &data[i]; 
         continue; 
       } 
       if(data[i] =='\x1D') 
       { 
         *lastdel = (&data[i] - lastdel-1 >255) ?(unsigned char) 255 : &data[i] - lastdel-1; 
         i++; 
         lastdel = &data[i]; 
         continue; 
       } 
       if(data[i] =='\x1E'|| data[i] =='\x1C') 
       { 
         if(*lastdel >(unsigned char) 254 )printf(" %c <++++~~~++++++++#######-------\n", *lastdel); 
         *lastdel = (&data[i] - lastdel-1 >255) ? (unsigned char) 255 : &data[i] - lastdel-1; 
         lastdel = &data[i]; 
         if(*lastdel >(unsigned char) 254 )printf(" %c <++++~~~++++++++#######-------\n", *lastdel); 
         continue; 
       } 
     } 
} 
int main(void) 
{ 
     //readFile("/root/20101202.174715.std"); 
     unsigned long s=290; 
     printf("hex: %x ", s<<24); 
       printf(" %x ", s<<16); 
       printf(" %x ", s<<8); 
       printf(" %x \n", s); 
     //exit(1); 
     int length ; 
     //unsigned char *bytes =readFile("/root/20101202.174715.std"); 
     unsigned char bytes[] = 
"\x31\x02\x00\x00\x67\x10\x00\x00\x00\x53\x02\x1E\x31\x1C\x36\x33\x1E\x37\x34\x1C\x55\x1E\x38\x1C\x44\x45\x30\x30\x30\x4C\x53\x38\x30\x35\x38\x36\x2E\x4C\x55\x53\x1E\x35\x1C\x38\x2E\x1D\x1E\x32\x38\x1C\x30\x2E\x36\x32\x30\x30\x1E\x33\x30\x1C\x30\x2E\x35\x39\x30\x30\x1E\x32\x36\x1C\x31\x35\x3A\x30\x33\x3A\x30\x34\x03\x02\x1E\x31\x1C\x36\x33\x1E\x37\x34\x1C\x55\x1E\x38\x1C\x44\x45\x30\x30\x30\x53\x46\x44\x30\x5A\x32\x36\x2E\x4C\x55\x53\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x30\x31\x32\x33\x34\x35\x36\x37\x38\x39\x1E\x35\x1C\x38\x2E\x1D\x1E\x32\x38\x1C\x31\x30\x2E\x30\x35\x38\x30\x1E\x33\x30\x1C\x31\x30\x2E\x30\x32\x38\x30\x1E\x32\x36\x1C\x31\x35\x3A\x30\x33\x3A\x30\x34\x03\x02\x1E\x31\x1C\x36\x33\x1E\x37\x34\x1C\x55\x1E\x38\x1C\x45\x55\x52\x4E\x4F\x4B\x2E\x46\x58\x56\x57\x44\x1E\x35\x1C\x31\x30\x2E\x1D\x1E\x33\x30\x1C\x37\x2E\x39\x35\x37\x31\x1E\x32\x38\x1C\x37\x2E\x39\x36\x32\x36\x1E\x38\x30\x1C\x37\x2E\x39\x35\x39\x38\x35\x1E\x37\x35\x32\x1C\x5A\x4B\x42\x5A\x1E\x32\x38\x31\x1C\x31\x35\x3A\x30\x33\x3A\x30\x34\x1E\x32\x36\x1C\x31\x35\x3A\x30\x33\x3A\x30\x34\x1E\x36\x34\x1C\x2D\x30\x2E\x30\x33\x39\x32\x1E\x31\x36\x34\x1C\x2D\x2E\x34\x38\x39\x34\x03\x45\x49\x00\x00\x00\x68\x10\x00\x00\x00\x53\x02\x1E\x31\x1C\x36\x33\x1E\x37\x34\x1C\x55\x1E\x38\x1C\x44\x45\x30\x30\x30\x39\x37\x36\x39\x37\x36\x30\x2E\x4C\x55\x53\x1E\x35\x1C\x31\x2E\x1D\x1E\x32\x38\x1C\x31\x30\x30\x2E\x38\x39\x30\x30\x1E\x33\x30\x1C\x31\x30\x30\x2E\x30\x39\x30\x30\x1E\x32\x36\x1C\x31\x35\x3A\x30\x33\x3A\x30\x34\x03\x45" 
; 
    /* Speicher fuer String mit 4294967296 Zeichen reservieren */ 
    unsigned char *data; 
    if ((data = (unsigned char *) malloc(1000000000 * sizeof(unsigned char))) == NULL) 
    { 
      printf("Nicht genug Speicher, um den Puffer zu allokieren\n"); 
      exit(1); 
    } 
    printf("Speicher fuer String wurde reserviert!\n"); 
    int strsize =((sizeof(bytes)/sizeof(*bytes))-1); 
    int pos =0; 
    int loop=1; 
    while(bytes[pos+9]=='S') 
    { 
      printf("----------------------------\n"); 
      printf("| LOOP %d, POSITION %d |\n", loop, pos); 
      printf("----------------------------\n\n"); 
      printf("hex: %x ", bytes[pos+0]<<24); 
      printf(" %x ", bytes[pos+1]<<16); 
      printf(" %x ", bytes[pos+2]<<8); 
      printf(" %x \n", bytes[pos+3]); 
      unsigned long size= ntohl(bytes[pos+0]<<24| bytes[pos+1]<<16| bytes[pos+2]<<8| bytes[pos+3]); 
      printf("=> RECOGNIZED SIZE: %lu \n", size); 
      printf("\n"); 
      int seq = ntohl(bytes[pos+4]<<24| bytes[pos+5]<<16| bytes[pos+6]<<8| bytes[pos+7]); 
      printf("seq number: %d \n", seq); 
      printf("compressed: %d \n", bytes[pos+8]); 
      printf("start in hex: %x, in char: %c \n", bytes[pos+9], bytes[pos+9]); 
      //printf("HeaderFieldIdentifier: %c %c %c \n", bytes[pos+10], bytes[pos+11], bytes[pos+12]); 
      printf("stop in hex: %x, in char: %c \n\n", bytes[pos+size+10], bytes[pos+size+10]); 
      /* Array kreieren das nur auf die komprimierten Daten zeigt */ 
      unsigned char *ptr; 
      ptr = &bytes[pos+10]; // Position des 1. Bytes 
      bytes[pos+size+10]='\0'; // Ende des Strings festlegen 
      /* Jetzt entkomprimieren wir die Daten */ 
      int ret=0; 
      unsigned long size_uncompress = size;//1000000000 * sizeof(unsigned char); 
      if(bytes[pos+8]=='\x01') 
      { 
        size_uncompress = 1000000000 * sizeof(unsigned char); 
        ret=uncompress(data, &size_uncompress, ptr, size); 
        data[size_uncompress]='\0'; 
      } 
      else 
      data = ptr; 
      //data[size_uncompress]='\0'; 
      printf("%d|%lu|%lu|%x|%x|%x|%x\n",ret,size,size_uncompress,ptr[0],ptr[1],bytes[pos+10],bytes[pos+11]); 
      printf("\n"); 
      printf("----------------------------\n"); 
      printf("|  Message as String: |\n"); 
      printf("----------------------------\n"); 
      printf("%s\n", data); 
      int i =0; 
      printf("\n"); 
      printf("----------------------------\n"); 
      printf("| Message as hexadecimal |\n"); 
      printf("----------------------------\n"); 
      for (i=0;i<size_uncompress ;i++) 
      { 
        printf("%x ",data[i]); 

      } 
      printf("\n\n"); 
      printf("----------------------------\n"); 
      printf("|  Edited message  |\n"); 
      printf("----------------------------\n"); 
      process(data, size_uncompress); 
      for (i=0;i<size_uncompress ;i++) 
      { 
        printf("%x ",data[i]); 
      } 
      printf("\n"); 
      pos+=(size+11); 
      loop++; 
    } 
    //free(data); 
} 

输出 Orig。消息

02 01 31 02 36 33 02 37 34 01 55 01 38 10 44 45 30 30 30 4c 53 38 30 35 38 36 2e 4c 55 53 01 35 02 38 2e 1d 02 32 38 06 30 2e 36 32 30 30 02 33 30 06 30 2e 35 39 30 30 02 32 36 08 31 35 3a 30 33 3a 30 34 03 02 01 31 02 36 33 02 37 34 01 55 01 38 ff 44 45 30 30 30 53 46 44 30 5a 32 36 2e 4c 55 53 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 **01** 35 02 38 2e 1d 02 32 38 07 31 30 2e 30 35 38 30 02 33 30 07 31 30 2e 30 32 38 30 02 32 36 08 31 35 3a 30 33 3a 30 34 03 02 01 31 02 36 33 02 37 34 01 55 01 38 c 45 55 52 4e 4f 4b 2e 46 58 56 57 44 01 35 03 31 30 2e 1d 02 33 30 06 37 2e 39 35 37 31 02 32 38 06 37 2e 39 36 32 36 02 38 30 07 37 2e 39 35 39 38 35 03 37 35 32 4 5a 4b 42 5a 03 32 38 31 8 31 35 3a 30 33 3a 30 34 02 32 36 8 31 35 3a 30 33 3a 30 34 02 36 34 07 2d 30 2e 30 33 39 32 03 31 36 34 06 2d 2e 34 38 39 34 3                                              
Replaced message                   
02 1E 31 1C 36 33 1E 37 34 1C 55 1E 38 1C 44 45 30 30 30 4C 53 38 30 35 38 36 2E 4C 55 53 1E 35 1C 38 2E 1D 1E 32 38 1C 30 2E 36 32 30 30 1E 33 30 1C 30 2E 35 39 30 30 1E 32 36 1C 31 35 3A 30 33 3A 30 34 03 02 1E 31 1C 36 33 1E 37 34 1C 55 1E 38 1C 44 45 30 30 30 53 46 44 30 5A 32 36 2E 4C 55 53 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 30 31 32 33 34 35 36 37 38 39 **1E** 35 1C 38 2E 1D 1E 32 38 1C 31 30 2E 30 35 38 30 1E 33 30 1C 31 30 2E 30 32 38 30 1E 32 36 1C 31 35 3A 30 33 3A 30 34 03 02 1E 31 1C 36 33 1E 37 34 1C 55 1E 38 1C 45 55 52 4E 4F 4B 2E 46 58 56 57 44 1E 35 1C 31 30 2E 1D 1E 33 30 1C 37 2E 39 35 37 31 1E 32 38 1C 37 2E 39 36 32 36 1E 38 30 1C 37 2E 39 35 39 38 35 1E 37 35 32 1C 5A 4B 42 5A 1E 32 38 31 1C 31 35 3A 30 33 3A 30 34 1E 32 36 1C 31 35 3A 30 33 3A 30 34 1E 36 34 1C 2D 30 2E 30 33 39 32 1E 31 36 34 1C 2D 2E 34 38 39 34 03 45 49 00 00 00 68 10 00 00 00 53 02 1E 31 1C 36 33 1E 37 34 1C 55 1E 38 1C 44 45 30 30 30 39 37 36 39 37 36 30 2E 4C 55 53 1E 35 1C 31 2E 1D 1E 32 38 1C 31 30 30 2E 38 39 30 30 1E 33 30 1C 31 30 30 2E 30 39 30 30 1E 32 36 1C 31 35 3A 30 33 3A 30 34 

Answer 1

首先，你检查，如果没有取代了以前的分离器（* lastdel）为255，因为它并没有被取代，不知道的情况下不会发生。然后你替换* lastdel 255，和更换当你改变了lastdel指针的值到下一个位置（尚未改变），你是否该位置被替换，并包含255 ...

难怪这种情况从未发生过。只要把测试放在正确的地方，它应该可以正常工作。