script generating lookup table for base64 decoding

b64_lookup_gen.c

#include <stdint.h>
#include <stdio.h>

void pprint(uint8_t* arr, int size)
{
    printf("uint8_t lookup[%d] = {", size);
    for(int i = 0; i < size-1; ++i) {
        printf("%u,", arr[i]);
    }
    printf("%u};\n", arr[size - 1]);
}

#define MAX_VALID 63; // 0b00111111
#define PAD 128;      // 0b10000000
#define INVALID 64;   // 0b01000000
// PAD and INVALID bitflags are convienient for error checking

int main()
{
    uint8_t lookup[256] = {0};
    int n = 0;
    for(int i = 'A'; i<='Z'; ++i) {
        lookup[i] = n++;
    }
    for(int i = 'a'; i<='z'; ++i) {
        lookup[i] = n++;
    }
    for(int i = '0'; i<='9'; ++i) {
        lookup[i] = n++;
    }
    lookup['+'] = n++;
    lookup['/'] = n++;
    
    lookup['='] = PAD;
    for(int i = 0; i<256; ++i) {
        if(lookup[i] == 0 && i != 'A') lookup[i] = INVALID;
    }

    pprint(lookup, 256);
}