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FEAT: support for Ascii85 (Base85) encoding
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`Ascii85` is a form of binary-to-text encoding used for example in PDF files.
One can now use 85 as a `base` value in `debase` and `enbase` functions:

```
>> enbase/base "Lion" 85
== "9PJE_"

>> debase/base "9PJE_" 85
== #{4C696F6E} ;== "Lion" if converted back to string
```

This addition is optional, requires compilation with `INCLUDE_BASE85` define.
Implements wish: Oldes/Rebol-issues#2410
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@Oldes
Oldes committed Mar 27, 2020
1 parent 6395779 commit 628234c
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1 change: 1 addition & 0 deletions make/make-settings.r
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Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,7 @@ Defines: [
USE_MIDI_DEVICE ;-- includes MIDI device when possible (Windows & macOS)

;INCLUDE_TASK ;-- tasks are not implemented yet, so include it only on demand
INCLUDE_BASE85 ;-- adds support for enbase/debase with base 85 (ASCII85)

;@@ optional fine tuning:
;DO_NOT_NORMALIZE_MAP_KEYS
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4 changes: 2 additions & 2 deletions src/boot/natives.r
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Original file line number Diff line number Diff line change
Expand Up @@ -406,15 +406,15 @@ debase: native [
{Decodes binary-coded string (BASE-64 default) to binary value.}
value [binary! string!] {The string to decode}
/base {Binary base to use}
base-value [integer!] {The base to convert from: 64, 16, or 2}
base-value [integer!] {The base to convert from: 85, 64, 16, or 2}
/url {Base 64 Decoding with URL and Filename Safe Alphabet}
]

enbase: native [
{Encodes a string into a binary-coded string (BASE-64 default).}
value [binary! string!] {If string, will be UTF8 encoded}
/base {Binary base to use}
base-value [integer!] {The base to convert to: 64, 16, or 2}
base-value [integer!] {The base to convert to: 85, 64, 16, or 2}
/url {Base 64 Encoding with URL and Filename Safe Alphabet}
]

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287 changes: 286 additions & 1 deletion src/core/f-enbase.c
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Original file line number Diff line number Diff line change
Expand Up @@ -40,7 +40,7 @@
***********************************************************************/
{
#define BIN_ERROR (REBYTE)0x80
#define BIN_SPACE (REBYTE)0x40
#define BIN_SPACE (REBYTE)0x55
#define BIN_VALUE (REBYTE)0x3f
#define IS_BIN_SPACE(c) (Debase64[c] & BIN_SPACE)

Expand Down Expand Up @@ -279,6 +279,124 @@
/* 7F DEL */ BIN_ERROR,
};

#ifdef INCLUDE_BASE85
#define BASE85_DIGITS 5 /* log85 (2^32) is 4.9926740807112 */
/***********************************************************************
**
*/ static const REBYTE Debase85[128] =
/*
** Base-85 (ASCII85) binary decoder table.
**
***********************************************************************/
{
/* Control Chars */
BIN_ERROR,BIN_ERROR,BIN_ERROR,BIN_ERROR, /* 80 */
BIN_ERROR,BIN_ERROR,BIN_ERROR,BIN_ERROR,
BIN_SPACE,BIN_SPACE,BIN_SPACE,BIN_ERROR,
BIN_SPACE,BIN_SPACE,BIN_ERROR,BIN_ERROR,
BIN_ERROR,BIN_ERROR,BIN_ERROR,BIN_ERROR,
BIN_ERROR,BIN_ERROR,BIN_ERROR,BIN_ERROR,
BIN_ERROR,BIN_ERROR,BIN_ERROR,BIN_ERROR,
BIN_ERROR,BIN_ERROR,BIN_ERROR,BIN_ERROR,

/* 20 */ BIN_SPACE,
/* 21 ! */ 0,
/* 22 " */ 1,
/* 23 # */ 2,
/* 24 $ */ 3,
/* 25 % */ 4,
/* 26 & */ 5,
/* 27 ' */ 6,
/* 28 ( */ 7,
/* 29 ) */ 8,
/* 2A * */ 9,
/* 2B + */ 10,
/* 2C , */ 11,
/* 2D - */ 12,
/* 2E . */ 13,
/* 2F / */ 14,
/* 30 0 */ 15,
/* 31 1 */ 16,
/* 32 2 */ 17,
/* 33 3 */ 18,
/* 34 4 */ 19,
/* 35 5 */ 20,
/* 36 6 */ 21,
/* 37 7 */ 22,
/* 38 8 */ 23,
/* 39 9 */ 24,
/* 3A : */ 25,
/* 3B ; */ 26,
/* 3C < */ 27,
/* 3D = */ 28,
/* 3E > */ 29,
/* 3F ? */ 30,
/* 40 @ */ 31,
/* 41 A */ 32,
/* 42 B */ 33,
/* 43 C */ 34,
/* 44 D */ 35,
/* 45 E */ 36,
/* 46 F */ 37,
/* 47 G */ 38,
/* 48 H */ 39,
/* 49 I */ 40,
/* 4A J */ 41,
/* 4B K */ 42,
/* 4C L */ 43,
/* 4D M */ 44,
/* 4E N */ 45,
/* 4F O */ 46,
/* 50 P */ 47,
/* 51 Q */ 48,
/* 52 R */ 49,
/* 53 S */ 50,
/* 54 T */ 51,
/* 55 U */ 52,
/* 56 V */ 53,
/* 57 W */ 54,
/* 58 X */ 55,
/* 59 Y */ 56,
/* 5A Z */ 57,
/* 5B [ */ 58,
/* 5C \ */ 59,
/* 5D ] */ 60,
/* 5E ^ */ 61,
/* 5F _ */ 62,
/* 60 ` */ 63,
/* 61 a */ 64,
/* 62 b */ 65,
/* 63 c */ 66,
/* 64 d */ 67,
/* 65 e */ 68,
/* 66 f */ 69,
/* 67 g */ 70,
/* 68 h */ 71,
/* 69 i */ 72,
/* 6A j */ 73,
/* 6B k */ 74,
/* 6C l */ 75,
/* 6D m */ 76,
/* 6E n */ 77,
/* 6F o */ 78,
/* 70 p */ 79,
/* 71 q */ 80,
/* 72 r */ 81,
/* 73 s */ 82,
/* 74 t */ 83,
/* 75 u */ 84,
/* 76 v */ BIN_ERROR,
/* 77 w */ BIN_ERROR,
/* 78 x */ BIN_ERROR,
/* 79 y */ BIN_ERROR,
/* 7A z */ BIN_ERROR,
/* 7B { */ BIN_ERROR,
/* 7C | */ BIN_ERROR,
/* 7D } */ BIN_ERROR,
/* 7E ~ */ BIN_ERROR,
/* 7F DEL */ BIN_ERROR
};
#endif

/***********************************************************************
**
Expand Down Expand Up @@ -307,6 +425,22 @@
};


#ifdef INCLUDE_BASE85
/***********************************************************************
**
*/ static const REBYTE Enbase85[85] =
/*
** Base-85 binary encoder table.
**
***********************************************************************/
{
"!\"#$%&'()*+,-./0123456789:;<=>?@"
"ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_`"
"abcdefghijklmnopqrstu"
};
#endif


/***********************************************************************
**
*/ static REBSER *Decode_Base2(const REBYTE **src, REBCNT len, REBYTE delim)
Expand Down Expand Up @@ -511,6 +645,89 @@
}


#ifdef INCLUDE_BASE85
/***********************************************************************
**
*/ static REBSER *Decode_Base85(const REBYTE **src, REBCNT len, REBYTE delim)
/*
***********************************************************************/
{
REBYTE *bp;
const REBYTE *cp;
REBSER *ser;
REBCNT ser_size;
REBCNT chunk;
REBCNT pos, c;
REBINT pad=0;

// Allocate buffer large enough to hold result:
ser = Make_Binary(((len + 4) / 5) * 4);
ser_size = SERIES_AVAIL(ser);

bp = STR_HEAD(ser);
cp = *src;

pos = 0;
while(len > 0) {
if(pos >= ser_size) {
// in extreme cases (a lot of 'z' chars) initialy computed size may not be enough
SERIES_TAIL(ser) = ser_size; // sets current series' tail (used by expand function bellow)
Expand_Series(ser, ser_size, 8); // may expand more than 8 bytes
bp = STR_HEAD(ser); // because above could reallocate
ser_size = SERIES_AVAIL(ser);
}
/* 'z' is a special way to encode 4 bytes of 0s */
if(*cp=='z') {
cp++;
len--;
bp[pos++] = 0u;
bp[pos++] = 0u;
bp[pos++] = 0u;
bp[pos++] = 0u;
continue;
}
chunk = 0;
for(c=0; c<BASE85_DIGITS; c++) {
REBYTE d = 0;
if(len > 0) {
len--;
d=Debase85[(REBYTE)*cp++];
if (d == BIN_SPACE) {
// ignore spaces
c--; continue;
}
if (d > 127) goto err; /* failure - invalid character */
}
else {
if(!pad) chunk++;
pad++;
}
if(c == 4) {
// math overflow checking.. for example input: {s8W-"}
if (chunk > (MAX_U32 / 85u)) goto err;
chunk *= 85;
if (chunk > (MAX_U32 - d)) goto err;
chunk += d;
} else chunk = chunk * 85 + d;
}
bp[pos ] = (REBYTE)(chunk >> 24);
bp[pos+1] = (REBYTE)(chunk >> 16);
bp[pos+2] = (REBYTE)(chunk >> 8);
bp[pos+3] = (REBYTE)(chunk );
pos += 4;
}
bp[pos] = 0;
ser->tail = pos - pad;
return ser;

err:
Free_Series(ser);
*src = cp;
return 0;
}
#endif


/***********************************************************************
**
*/ const REBYTE *Decode_Binary(REBVAL *value, const REBYTE *src, REBCNT len, REBINT base, REBYTE delim, REBOOL urlSafe)
Expand All @@ -531,6 +748,13 @@
case 2:
ser = Decode_Base2 (&src, len, delim);
break;
case 85:
#ifdef INCLUDE_BASE85
ser = Decode_Base85 (&src, len, delim);
#else
Trap0(RE_FEATURE_NA);
#endif
break;
}

if (!ser) return 0;
Expand Down Expand Up @@ -674,3 +898,64 @@

return series;
}


#ifdef INCLUDE_BASE85
/***********************************************************************
**
*/ REBSER *Encode_Base85(REBVAL *value, REBSER *series, REBFLG brk)
/*
** Base85 encode a given series. Must be BYTES, not UNICODE.
**
***********************************************************************/
{
REBCNT len;
REBYTE *bp;
REBYTE *src;
REBCNT x=0;
REBINT loop;
REBCNT i, chunk;

len = VAL_LEN(value);
src = VAL_BIN_DATA(value);

// Account for hex, lines, and extra syntax:
series = Prep_String(series, &bp, ((len + 3) / 4) * 5);
// (Note: tail not properly set yet)

//if (len >= 32 && brk) *bp++ = LF;
loop = (len / 4) - 1;
if(loop >= 0) {
for (x = 0; x <= 4 * loop;) {
chunk = ((REBCNT)src[x++]) << 24u;
chunk |= ((REBCNT)src[x++]) << 16u;
chunk |= ((REBCNT)src[x++]) << 8u;
chunk |= ((REBCNT)src[x++]) ;
if(chunk==0) {
*bp++='z'; /* this is a special zero character */
} else {
for(i = BASE85_DIGITS;i--;) {
bp[i] = Enbase85[chunk%85];
chunk /= 85;
}
bp += 5;
}
}
}
if ((len % 4) != 0) {
chunk = (((REBCNT)src[x++]) << 24u);
chunk |= ((x < (REBCNT)len) ? (((REBCNT)src[x++]) << 16u): 0u);
chunk |= ((x < (REBCNT)len) ? (((REBCNT)src[x++]) << 8u): 0u);
chunk |= ((x < (REBCNT)len) ? (((REBCNT)src[x++]) ): 0u);
for(i = BASE85_DIGITS;i--;) {
bp[i] = Enbase85[chunk%85];
chunk /= 85;
}
bp += (len % 4) + 1;
}
*bp = 0;
SERIES_TAIL(series) = DIFF_PTRS(bp, series->data);

return series;
}
#endif
8 changes: 8 additions & 0 deletions src/core/n-strings.c
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Original file line number Diff line number Diff line change
Expand Up @@ -497,6 +497,14 @@ static struct digest {
break;
case 2:
ser = Encode_Base2(arg, 0, FALSE);
break;
case 85:
#ifdef INCLUDE_BASE85
ser = Encode_Base85(arg, 0, FALSE);
#else
Trap0(RE_FEATURE_NA);
#endif

break;
default:
Trap_Arg(D_ARG(3));
Expand Down
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