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decrease encode time

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The functions encode and decode are now capable of processing larger
buffers with less conditional logic. Input and output functions need to
follow suit to make better use of this next. Encode without line
wrapping already makes use of these improvements, because input and
output are now entirely handled by <stdio.h> functions.
This commit is contained in:
Eric 2025-05-28 23:24:05 +02:00
parent 3194981825
commit f0577d8ea0
4 changed files with 58 additions and 71 deletions
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101
encode.c
View file

@ -7,80 +7,83 @@ unsigned char b64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
"0123456789" \
"+/";
unsigned char b64u[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
"abcdefghijklmnopqrstuvwxyz" \
"0123456789" \
"-_";
unsigned char b64url[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ" \
"abcdefghijklmnopqrstuvwxyz" \
"0123456789" \
"-_";
int
encode(unsigned char *op, int olen, unsigned char *sp, int url)
{
int n;
unsigned char *sb, *enc;
int tmp;
unsigned char *table;
unsigned char *sbeg;
unsigned char *tend;
sb = sp;
enc = (!url) ? b64 : b64u;
switch (olen) {
case 3:
*sp++ = enc[(*op & ~3) >> 2];
n = (*op++ & 3) << 4;
*sp++ = enc[n + ((*op & ~15) >> 4)];
n = (*op++ & 15) << 2;
*sp++ = enc[n + ((*op & 192) >> 6)];
*sp = enc[*op & ~192];
break;
table = (!url) ? b64 : b64url;
sbeg = sp;
tend = op + olen - (olen % 3);
while (op < tend) {
*sp++ = table[(*op & ~3) >> 2];
tmp = (*op++ & 3) << 4;
*sp++ = table[tmp + ((*op & ~15) >> 4)];
tmp = (*op++ & 15) << 2;
*sp++ = table[tmp + ((*op & 192) >> 6)];
*sp++ = table[*op++ & ~192];
}
switch (olen % 3) {
case 2:
*sp++ = enc[(*op & ~3) >> 2];
n = (*op++ & 3) << 4;
*sp++ = enc[n + ((*op & ~15) >> 4)];
*sp++ = enc[(*op & 15) << 2];
*sp = PADDING;
*sp++ = table[(*op & ~3) >> 2];
tmp = (*op++ & 3) << 4;
*sp++ = table[tmp + ((*op & ~15) >> 4)];
*sp++ = table[(*op & 15) << 2];
*sp++ = PADDING;
break;
case 1:
*sp++ = enc[(*op & ~3) >> 2];
*sp++ = enc[(*op & 3) << 4];
*sp++ = table[(*op & ~3) >> 2];
*sp++ = table[(*op & 3) << 4];
*sp++ = PADDING;
*sp++ = PADDING;
*sp = PADDING;
break;
}
return sp-sb+1;
return sp-sbeg;
}
int
decode(unsigned char *sp, int slen, unsigned char *op, int url)
{
int n, b, atob(int c, int url);
unsigned char *ob;
int tmp, b, atob(int c, int url);
unsigned char *obeg;
unsigned char *qend;
ob = op;
switch (slen) {
case 4:
n = atob(*sp++, url) << 2;
b = atob(*sp++, url);
*op++ = n + ((b & ~15) >> 4);
n = (b & 15) << 4;
b = atob(*sp++, url);
*op++ = n + ((b & ~3) >> 2);
*op = ((b & 3) << 6) + atob(*sp, url);
break;
obeg = op;
qend = sp + slen - (slen % 4);
while (sp < qend) {
tmp = atob(*sp++, url) << 2;
b = atob(*sp++, url);
*op++ = tmp + ((b & ~15) >> 4);
tmp = (b & 15) << 4;
b = atob(*sp++, url);
*op++ = tmp + ((b & ~3) >> 2);
*op++ = ((b & 3) << 6) + atob(*sp++, url);
}
switch (slen % 4) {
case 3:
n = atob(*sp++, url) << 2;
tmp = atob(*sp++, url) << 2;
b = atob(*sp++, url);
*op++ = n + ((b & ~15) >> 4);
n = (b & 15) << 4;
*op = n + ((atob(*sp, url) & ~3) >> 2);
*op++ = tmp + ((b & ~15) >> 4);
tmp = (b & 15) << 4;
*op++ = tmp + ((atob(*sp++, url) & ~3) >> 2);
break;
case 2:
n = atob(*sp++, url) << 2;
*op = n + ((atob(*sp, url) & ~15) >> 4);
tmp = atob(*sp++, url) << 2;
*op++ = tmp + ((atob(*sp++, url) & ~15) >> 4);
break;
}
return op-ob+1;
return op-obeg;
}
int atob(int c, int url)