/*
   begin library headers
 */

/*
   cdecode.h - c header for a base64 decoding algorithm

   This is part of the libb64 project, and has been placed in the public domain.
   For details, see http://sourceforge.net/projects/libb64
 */
#ifndef BASE64_CDECODE_H
#define BASE64_CDECODE_H

typedef enum {
    step_a, step_b, step_c, step_d
} base64_decodestep;

typedef struct {
    base64_decodestep step;
    char plainchar;
} base64_decodestate;

void base64_init_decodestate(base64_decodestate *state_in);

int base64_decode_value(char value_in);

int base64_decode_block(const char *code_in, const int length_in, char *plaintext_out,
                        base64_decodestate *state_in);

#endif /* BASE64_CDECODE_H */

/*
   end library headers
 */

#include "ua_base64.h"

UA_Int32 UA_base64_getDecodedSize(UA_String *const base64EncodedData) {
    //note that base64-encoded data length is always divisible by 4
    UA_Int32 temp = base64EncodedData->length * 3 / 4;

    //subtract padding
    if(base64EncodedData->data[base64EncodedData->length-1] == '=') {
        temp--;
        if(base64EncodedData->data[base64EncodedData->length-2] == '=')
            temp--;
    }

    return temp;
}

UA_Int32 UA_base64_decode(UA_String *const base64EncodedData, UA_Byte *target) {
    if(target == UA_NULL)
        return UA_ERROR;
    base64_decodestate state;
    base64_init_decodestate(&state);
    base64_decode_block((char *)(base64EncodedData->data), base64EncodedData->length, (char *)target, &state);
    return UA_NO_ERROR;
}

/*
   begin library code
 */

/*
   cdecoder.c - c source to a base64 decoding algorithm implementation

   This is part of the libb64 project, and has been placed in the public domain.
   For details, see http://sourceforge.net/projects/libb64
 */

int base64_decode_value(char value_in) {
    static const char decoding[]    =
    { 62, -1,   -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, -1, 0,  1,  2,  3,
      4,  5,
      6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26,
      27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51 };
    static const char decoding_size = sizeof(decoding);
    value_in -= 43;
    if(value_in > decoding_size) return -1;
    return decoding[(int)value_in];
}

void base64_init_decodestate(base64_decodestate *state_in) {
    state_in->step      = step_a;
    state_in->plainchar = 0;
}

int base64_decode_block(const char *code_in, const int length_in, char *plaintext_out,
                        base64_decodestate *state_in) {
    const char *codechar  = code_in;
    char       *plainchar = plaintext_out;
    signed char fragment;

    *plainchar = state_in->plainchar;

    switch(state_in->step) {
        while(1) {
        case step_a:
            do {
                if(codechar == code_in+length_in) {
                    state_in->step      = step_a;
                    state_in->plainchar = *plainchar;
                    return plainchar - plaintext_out;
                }
                fragment = (char)base64_decode_value(*codechar++);
            } while(fragment < 0);
            *plainchar = (fragment & 0x03f) << 2;

        case step_b:
            do {
                if(codechar == code_in+length_in) {
                    state_in->step      = step_b;
                    state_in->plainchar = *plainchar;
                    return plainchar - plaintext_out;
                }
                fragment = (char)base64_decode_value(*codechar++);
            } while(fragment < 0);
            *plainchar++ |= (fragment & 0x030) >> 4;
            *plainchar    = (fragment & 0x00f) << 4;

        case step_c:
            do {
                if(codechar == code_in+length_in) {
                    state_in->step      = step_c;
                    state_in->plainchar = *plainchar;
                    return plainchar - plaintext_out;
                }
                fragment = (char)base64_decode_value(*codechar++);
            } while(fragment < 0);
            *plainchar++ |= (fragment & 0x03c) >> 2;
            *plainchar    = (fragment & 0x003) << 6;

        case step_d:
            do {
                if(codechar == code_in+length_in) {
                    state_in->step      = step_d;
                    state_in->plainchar = *plainchar;
                    return plainchar - plaintext_out;
                }
                fragment = (char)base64_decode_value(*codechar++);
            } while(fragment < 0);
            *plainchar++ |= (fragment & 0x03f);
        }
    }
    /* control should not reach here */
    return plainchar - plaintext_out;
}