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/*
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
*/
#include <cdecode.h>
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 < 0 || 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;
}
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