如何将char数组转换为十六进制

Question

我想将用户填充的 char 数组（如下面代码中的 part1）转换为十六进制。其实就是将两个char转换成一个十六进制char.

char part1[2];
char ans;
part1[0]='f';
part1[1]='2';

现在我可以像这样将 part1 十六进制转换为字符 ans：

ans=0xf2;

Answer 1

第 1 步：将每个文本字符解析为数字：

unsigned int parse_char(char c)
{
    if ('0' <= c && c <= '9') return c - '0';
    if ('a' <= c && c <= 'f') return 10 + c - 'a';
    if ('A' <= c && c <= 'F') return 10 + c - 'A';

    abort();
}

第 2 步：使用数学计算 assemble 结果，遵循位值表示法规则：

unsigned char ans = parse_char(part1[0]) * 0x10 + parse_char(part1[1]);

Answer 2

这是可能的解决方案：

unsigned char CharToHex( char c )
{
    switch( c ) {
        case '0': return 0;
        case '1': return 1;
        case '2': return 2;
        case '3': return 3;
        case '4': return 4;
        case '5': return 5;
        case '6': return 6;
        case '7': return 7;
        case '8': return 8;
        case '9': return 9;
        case 'a': case 'A': return 10;
        case 'b': case 'B': return 11;
        case 'c': case 'C': return 12;
        case 'd': case 'D': return 13;
        case 'e': case 'E': return 14;
        case 'f': case 'F': return 15;
    }
    return 16;
}

// return 0 if error occurred
int Convert( const char* source, char* dest )
{
    for( int i = 0; source[i] != '[=10=]' && source[i + 1] != '[=10=]'; i += 2 ) {
        unsigned char  hex1 = CharToHex( source[i] );
        unsigned char  hex2 = CharToHex( source[i + 1] );
        if( hex1 == 16 || hex2 == 16 ) {
            return 0;
        }
        *dest = ( char )( hex1 << 4 | hex2 );
        dest++;
    }
    return 1;
}

更新：

这些是将 char 转换为十六进制数字的方法：

// variant 1
unsigned char CharToHex( char c )
{
    if( c >= '0' && c <= '9' ) {
        return ( c - '0' );
    }
    if( c >= 'a' && c <= 'f' ) {
        return ( c - 'a' + 10 );
    }
    if( c >= 'A' && c <= 'F' ) {
        return ( c - 'A' + 10 );
    }
    return 16;
}
// variant 2
unsigned char CharToHex( char c )
{
    c = tolower( c );
    if( c >= '0' && c <= '9' ) {
        return ( c - '0' );
    }
    if( c >= 'a' && c <= 'f' ) {
        return ( c - 'a' + 10 );
    }
    return 16;
}
// variant 3
unsigned char CharHexConversionTable[256] = {
    // ascii
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
     0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 16, 16, 16, 16, 16, 16,
    16, 10, 11, 12, 13, 14, 15, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 10, 11, 12, 13, 14, 15, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    // rest
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16,
    16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16, 16
};
unsigned char CharToHex( char c )
{
    return CharHexConversionTable[(unsigned char)c];
}

如何将char数组转换为十六进制

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