無符號字符比較

Question

我有附加代碼的問題。我希望用偏移量（它們之間的字節量）替換一些分隔符。我只有1個字節，如果偏移量大於254，我想用255替換它。在這種情況下，下一個找到的偏移量不應該被替換。替換部分工作正常...無論如何我無法識別是否最後一個分隔符被替換爲255最後一次，它被跳過或轉換，我不知道爲什麼/我在做什麼錯誤。也許任何人都可以給我任何線索。這裏的代碼和最後的輸出。我用（**）標記了分隔符，不應該被替換。

#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); 
} 

輸出 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，你檢查，如果沒有取代了以前的分離器（* lastdel）爲255，因爲它並沒有被取代，不知道的情況下不會發生。然後你替換* lastdel 255，和更換當你改變了lastdel指針的值到下一個位置（尚未改變），你是否該位置被替換，幷包含255 ...

難怪這種情況從未發生過。只要把測試放在正確的地方，它應該可以正常工作。