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[core] base64 encode w/ reduced data dependencies

This commit is contained in:
Glenn Strauss 2021-05-18 21:10:04 -04:00
parent e7805dbf93
commit 235c0dca84
1 changed files with 13 additions and 12 deletions
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25
src/base64.c
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@ -120,6 +120,7 @@ static size_t li_base64_decode(unsigned char * const result, const size_t out_le
size_t li_to_base64_no_padding(char* out, size_t out_length, const unsigned char* in, size_t in_length, base64_charset charset) {
size_t i;
size_t out_pos = 0;
uint_fast32_t v;
const char* const base64_table = (charset)
? base64_url_table /* BASE64_URL */
: base64_standard_table; /* BASE64_STANDARD */
@ -131,11 +132,11 @@ size_t li_to_base64_no_padding(char* out, size_t out_length, const unsigned char
force_assert((in_length+2)/3*4 <= out_length);
for (i = 2; i < in_length; i += 3) {
unsigned int v = (in[i-2] << 16) | (in[i-1] << 8) | in[i];
out[out_pos+3] = base64_table[v & 0x3f]; v >>= 6;
out[out_pos+2] = base64_table[v & 0x3f]; v >>= 6;
out[out_pos+1] = base64_table[v & 0x3f]; v >>= 6;
out[out_pos+0] = base64_table[v & 0x3f];
v = (in[i-2] << 16) | (in[i-1] << 8) | in[i];
out[out_pos+0] = base64_table[(v >> 18) & 0x3f];
out[out_pos+1] = base64_table[(v >> 12) & 0x3f];
out[out_pos+2] = base64_table[(v >> 6) & 0x3f];
out[out_pos+3] = base64_table[(v ) & 0x3f];
out_pos += 4;
}
@ -146,19 +147,19 @@ size_t li_to_base64_no_padding(char* out, size_t out_length, const unsigned char
case 1:
{
/* pretend in[i-1] = in[i] = 0, don't write last two (out_pos+3, out_pos+2) characters */
unsigned int v = (in[i-2] << 4);
out[out_pos+1] = base64_table[v & 0x3f]; v >>= 6;
out[out_pos+0] = base64_table[v & 0x3f];
v = (in[i-2] << 4);
out[out_pos+0] = base64_table[(v >> 6) & 0x3f];
out[out_pos+1] = base64_table[(v ) & 0x3f];
out_pos += 2;
}
break;
case 2:
{
/* pretend in[i] = 0, don't write last (out_pos+3) character */
unsigned int v = (in[i-2] << 10) | (in[i-1] << 2);
out[out_pos+2] = base64_table[v & 0x3f]; v >>= 6;
out[out_pos+1] = base64_table[v & 0x3f]; v >>= 6;
out[out_pos+0] = base64_table[v & 0x3f];
v = (in[i-2] << 10) | (in[i-1] << 2);
out[out_pos+0] = base64_table[(v >> 12) & 0x3f];
out[out_pos+1] = base64_table[(v >> 6) & 0x3f];
out[out_pos+2] = base64_table[(v ) & 0x3f];
out_pos += 3;
}
break;