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Implement, with help from glib base64 source, routines to turn binary

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into SMS-compatible strings and back.  This should ensure that the
format is cross-platform.
This commit is contained in:
ehouse 2009-01-05 02:08:55 +00:00
parent bf77466ea0
commit 47f6ab7da3
2 changed files with 143 additions and 3 deletions
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139
common/strutils.c
View file

@ -1,6 +1,7 @@
/* -*-mode: C; fill-column: 78; c-basic-offset: 4; -*- */
/* -*-mode: C; compile-command: "cd ../linux && make MEMDEBUG=TRUE"; -*- */
/*
* Copyright 2001 by Eric House (xwords@eehouse.org). All rights reserved.
* Copyright 2001-2009 by Eric House (xwords@eehouse.org). All rights
* reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@ -229,6 +230,140 @@ randIntArray( XP_U16* rnums, XP_U16 count )
return changed;
} /* randIntArray */
#ifdef XWFEATURE_SMS
/* base-64 encode binary data as a message legal for SMS. See
* http://www.ietf.org/rfc/rfc2045.txt for the algorithm. glib uses this and
* so it's not needed on linux, but unless all platforms provided identical
* implementations it's needed for messages to be cross-platform.
*/
static const XP_UCHAR*
getSMSTable( void )
{
return "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
}
#define PADCHAR '='
static void
bitsToChars( const XP_U8* bytesIn, XP_U16 nValidBytes, XP_UCHAR* out,
XP_U16* outlen )
{
XP_U16 nValidSextets = ((nValidBytes * 8) + 5) / 6; /* +5: round up */
XP_U8 local[4] = { 0, 0, 0, 0 };
XP_U16 bits[4];
XP_MEMCPY( local, bytesIn, nValidBytes );
/* top 6 bits of first byte */
bits[0] = local[0] >> 2;
/* bottom 2 bits of first byte, top four of second */
bits[1] = ((local[0] << 4) & 0x30 ) | (local[1] >> 4);
/* bottom four bits of second byte, top two of third */
bits[2] = ((local[1] << 2) & 0x3C) | (local[2] >> 6);
/* bottom six bits of third */
bits[3] = local[2] & 0x3F;
const XP_UCHAR* table = getSMSTable();
XP_U16 ii;
for ( ii = 0; ii < 4; ++ii ) {
XP_UCHAR ch;
if ( ii < nValidSextets ) {
XP_U16 index = bits[ii];
ch = table[index];
} else {
ch = PADCHAR;
}
out[(*outlen)++] = ch;
}
} /* bitsToChars */
void
binToSms( XP_UCHAR* out, XP_U16* outlenp, const XP_U8* in, const XP_U16 inlen )
{
XP_U16 inConsumed;
XP_U16 outlen = 0;
for ( inConsumed = 0; ; /*inConsumed += 3*/ ) {
XP_U16 validBytes = XP_MIN( 3, inlen - inConsumed );
bitsToChars( &in[inConsumed], validBytes, out, &outlen );
XP_ASSERT( outlen <= *outlenp );
inConsumed += 3;
if ( inConsumed >= inlen ) {
break;
}
}
XP_ASSERT( outlen < *outlenp );
out[outlen] = '\0';
*outlenp = outlen;
XP_ASSERT( *outlenp >= inlen );
} /* binToSms */
/* Return false if illegal, e.g. contains bad characters.
*/
static XP_U8
findRank( XP_UCHAR ch )
{
XP_U8 rank;
if ( ch == PADCHAR ) {
rank = 0;
} else {
const XP_UCHAR* table = getSMSTable();
for ( rank = 0; rank < 64; ++rank ) {
if ( table[rank] == ch ) {
break;
}
}
XP_ASSERT( rank < 64 );
}
return rank;
}
/* This function stolen from glib file glib/gbase64.c. It's also GPL'd, so
* that may not matter. But does my copyright need to change? PENDING
*
* Also, need to check there's space before writing! PENDING
*/
XP_Bool
smsToBin( XP_U8* out, XP_U16* outlenp, const XP_UCHAR* sms, XP_U16 smslen )
{
const XP_UCHAR* inptr;
XP_U8* outptr = out;
const XP_UCHAR* smsend = sms + smslen;
XP_U8 ch, rank;
XP_U8 last[2];
unsigned int vv = 0;
int ii = 0;
inptr = sms;
last[0] = last[1] = 0;
while ( inptr < smsend ) {
ch = *inptr++;
rank = findRank( ch );
last[1] = last[0];
last[0] = ch;
vv = (vv<<6) | rank;
if ( ++ii == 4 ) {
*outptr++ = vv >> 16;
if (last[1] != PADCHAR ) {
*outptr++ = vv >> 8;
}
if (last[0] != PADCHAR ) {
*outptr++ = vv;
}
ii = 0;
}
}
XP_ASSERT( *outlenp >= (outptr - out) );
*outlenp = outptr - out;
return XP_TRUE;
} /* smsToBin */
#endif
#ifdef DEBUG
#define NUM_PER_LINE 8
void

7
common/strutils.h
View file

@ -1,6 +1,7 @@
/* -*-mode: C; fill-column: 78; c-basic-offset: 4; -*- */
/*
* Copyright 2001 by Eric House (xwords@eehouse.org). All rights reserved.
* Copyright 2001-2009 by Eric House (xwords@eehouse.org). All rights
* reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
@ -82,6 +83,10 @@ XP_UCHAR* emptyStringIfNull( XP_UCHAR* str );
/* Produce an array of ints 0..count-1, juggled */
XP_Bool randIntArray( XP_U16* rnums, XP_U16 count );
#ifdef XWFEATURE_SMS
void binToSms( XP_UCHAR* out, XP_U16* outlen, const XP_U8* in, XP_U16 inlen );
XP_Bool smsToBin( XP_U8* out, XP_U16* outlen, const XP_UCHAR* in, XP_U16 inlen );
#endif
#ifdef DEBUG
void log_hex( const XP_U8*memp, XP_U16 len, const char* tag );