MIPS程序集 - 从具有十六进制值的文件中读取

Question

这里是我的问题。

我想使用MIPS程序集从txt/dat文件中读取数据。问题是文件中的每个文件都是十六进制的，例如0x54ebcda7。当我尝试读取并将其加载到寄存器中时，MARS模拟器用ascii值读取它。我不想要这个，需要那个十六进制数的“实际值”？我怎么做？

Answer 1

我只是要告诉这到底是怎么用C来完成，这应该是很容易为你翻译成MIPS汇编：

// Assume that data from the file has been read into a char *buffer 
// Assume that there's an int32_t *values where the values will be stored 

while (bufferBytes) { 
    c = *buffer++; 
    bufferBytes--; 

    // Consume the "0x" prefix, then read digits until whitespace is found 
    if (c == '0' && prefixBytes == 0) { 
     prefixBytes++; 
    } else if (c == 'x' && prefixBytes == 1) { 
     prefixBytes++; 
    } else { 
     if (c == ' ' || c == '\t' || c == '\n' || c == '\r') { 
      if (prefixBytes == 2) { 
       // Reached the end of a number. Store it and start over 
       prefixBytes = 0; 
       *values++ = currValue; 
       currValue = 0; 
      } else if (prefixBytes == 0) { 
       // IGNORE (whitespace in between numbers) 
      } else { 
       // ERROR 
      } 
     } else if (prefixBytes == 2) { 
      if (c >= '0' && c <= '9') { 
       c -= '0'; 
      } else if (c >= 'a' && c <= 'f') { 
       c -= ('a'-10); 
      } else if (c >= 'A' && c <= 'F') { 
       c -= ('A'-10); 
      } else { 
       // ERROR 
      } 
      currValue = (currValue << 4) | c; 
     } else { 
      // ERROR 
     } 
    } 
} 
// Store any pending value that was left when reaching the end of the buffer 
if (prefixBytes == 2) { 
    *values++ = currValue; 
}