From 79d16d72cd530acbee682ebee44d5b1d2010c661 Mon Sep 17 00:00:00 2001
From: Micah Anderson <micah@riseup.net>
Date: Sun, 17 Nov 2013 17:25:01 -0500
Subject: initial import of debian package to build with autobuilder

---
 encode.c | 245 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 245 insertions(+)
 create mode 100644 encode.c

(limited to 'encode.c')

diff --git a/encode.c b/encode.c
new file mode 100644
index 0000000..1410813
--- /dev/null
+++ b/encode.c
@@ -0,0 +1,245 @@
+/*
+** 2002 April 25
+**
+** The author disclaims copyright to this source code.  In place of
+** a legal notice, here is a blessing:
+**
+**    May you do good and not evil.
+**    May you find forgiveness for yourself and forgive others.
+**    May you share freely, never taking more than you give.
+**
+*************************************************************************
+** This file contains helper routines used to translate binary data into
+** a null-terminated string (suitable for use in SQLite) and back again.
+** These are convenience routines for use by people who want to store binary
+** data in an SQLite database.  The code in this file is not used by any other
+** part of the SQLite library.
+**
+** $Id: encode.c,v 1.2 2004/07/03 22:51:18 ghaering Exp $
+*/
+#include <string.h>
+
+/*
+** How This Encoder Works
+**
+** The output is allowed to contain any character except 0x27 (') and
+** 0x00.  This is accomplished by using an escape character to encode
+** 0x27 and 0x00 as a two-byte sequence.  The escape character is always
+** 0x01.  An 0x00 is encoded as the two byte sequence 0x01 0x01.  The
+** 0x27 character is encoded as the two byte sequence 0x01 0x03.  Finally,
+** the escape character itself is encoded as the two-character sequence
+** 0x01 0x02.
+**
+** To summarize, the encoder works by using an escape sequences as follows:
+**
+**       0x00  ->  0x01 0x01
+**       0x01  ->  0x01 0x02
+**       0x27  ->  0x01 0x03
+**
+** If that were all the encoder did, it would work, but in certain cases
+** it could double the size of the encoded string.  For example, to
+** encode a string of 100 0x27 characters would require 100 instances of
+** the 0x01 0x03 escape sequence resulting in a 200-character output.
+** We would prefer to keep the size of the encoded string smaller than
+** this.
+**
+** To minimize the encoding size, we first add a fixed offset value to each 
+** byte in the sequence.  The addition is modulo 256.  (That is to say, if
+** the sum of the original character value and the offset exceeds 256, then
+** the higher order bits are truncated.)  The offset is chosen to minimize
+** the number of characters in the string that need to be escaped.  For
+** example, in the case above where the string was composed of 100 0x27
+** characters, the offset might be 0x01.  Each of the 0x27 characters would
+** then be converted into an 0x28 character which would not need to be
+** escaped at all and so the 100 character input string would be converted
+** into just 100 characters of output.  Actually 101 characters of output - 
+** we have to record the offset used as the first byte in the sequence so
+** that the string can be decoded.  Since the offset value is stored as
+** part of the output string and the output string is not allowed to contain
+** characters 0x00 or 0x27, the offset cannot be 0x00 or 0x27.
+**
+** Here, then, are the encoding steps:
+**
+**     (1)   Choose an offset value and make it the first character of
+**           output.
+**
+**     (2)   Copy each input character into the output buffer, one by
+**           one, adding the offset value as you copy.
+**
+**     (3)   If the value of an input character plus offset is 0x00, replace
+**           that one character by the two-character sequence 0x01 0x01.
+**           If the sum is 0x01, replace it with 0x01 0x02.  If the sum
+**           is 0x27, replace it with 0x01 0x03.
+**
+**     (4)   Put a 0x00 terminator at the end of the output.
+**
+** Decoding is obvious:
+**
+**     (5)   Copy encoded characters except the first into the decode 
+**           buffer.  Set the first encoded character aside for use as
+**           the offset in step 7 below.
+**
+**     (6)   Convert each 0x01 0x01 sequence into a single character 0x00.
+**           Convert 0x01 0x02 into 0x01.  Convert 0x01 0x03 into 0x27.
+**
+**     (7)   Subtract the offset value that was the first character of
+**           the encoded buffer from all characters in the output buffer.
+**
+** The only tricky part is step (1) - how to compute an offset value to
+** minimize the size of the output buffer.  This is accomplished by testing
+** all offset values and picking the one that results in the fewest number
+** of escapes.  To do that, we first scan the entire input and count the
+** number of occurances of each character value in the input.  Suppose
+** the number of 0x00 characters is N(0), the number of occurances of 0x01
+** is N(1), and so forth up to the number of occurances of 0xff is N(255).
+** An offset of 0 is not allowed so we don't have to test it.  The number
+** of escapes required for an offset of 1 is N(1)+N(2)+N(40).  The number
+** of escapes required for an offset of 2 is N(2)+N(3)+N(41).  And so forth.
+** In this way we find the offset that gives the minimum number of escapes,
+** and thus minimizes the length of the output string.
+*/
+
+/*
+** Encode a binary buffer "in" of size n bytes so that it contains
+** no instances of characters '\'' or '\000'.  The output is 
+** null-terminated and can be used as a string value in an INSERT
+** or UPDATE statement.  Use sqlite_decode_binary() to convert the
+** string back into its original binary.
+**
+** The result is written into a preallocated output buffer "out".
+** "out" must be able to hold at least 2 +(257*n)/254 bytes.
+** In other words, the output will be expanded by as much as 3
+** bytes for every 254 bytes of input plus 2 bytes of fixed overhead.
+** (This is approximately 2 + 1.0118*n or about a 1.2% size increase.)
+**
+** The return value is the number of characters in the encoded
+** string, excluding the "\000" terminator.
+*/
+int sqlite_encode_binary(const unsigned char *in, int n, unsigned char *out){
+  int i, j, e = 0, m;
+  int cnt[256];
+  if( n<=0 ){
+    out[0] = 'x';
+    out[1] = 0;
+    return 1;
+  }
+  memset(cnt, 0, sizeof(cnt));
+  for(i=n-1; i>=0; i--){ cnt[in[i]]++; }
+  m = n;
+  for(i=1; i<256; i++){
+    int sum;
+    if( i=='\'' ) continue;
+    sum = cnt[i] + cnt[(i+1)&0xff] + cnt[(i+'\'')&0xff];
+    if( sum<m ){
+      m = sum;
+      e = i;
+      if( m==0 ) break;
+    }
+  }
+  out[0] = e;
+  j = 1;
+  for(i=0; i<n; i++){
+    int c = (in[i] - e)&0xff;
+    if( c==0 ){
+      out[j++] = 1;
+      out[j++] = 1;
+    }else if( c==1 ){
+      out[j++] = 1;
+      out[j++] = 2;
+    }else if( c=='\'' ){
+      out[j++] = 1;
+      out[j++] = 3;
+    }else{
+      out[j++] = c;
+    }
+  }
+  out[j] = 0;
+  return j;
+}
+
+/*
+** Decode the string "in" into binary data and write it into "out".
+** This routine reverses the encoding created by sqlite_encode_binary().
+** The output will always be a few bytes less than the input.  The number
+** of bytes of output is returned.  If the input is not a well-formed
+** encoding, -1 is returned.
+**
+** The "in" and "out" parameters may point to the same buffer in order
+** to decode a string in place.
+*/
+int sqlite_decode_binary(const unsigned char *in, unsigned char *out){
+  int i, c, e;
+  e = *(in++);
+  i = 0;
+  while( (c = *(in++))!=0 ){
+    if( c==1 ){
+      c = *(in++);
+      if( c==1 ){
+        c = 0;
+      }else if( c==2 ){
+        c = 1;
+      }else if( c==3 ){
+        c = '\'';
+      }else{
+        return -1;
+      }
+    }
+    out[i++] = (c + e)&0xff;
+  }
+  return i;
+}
+
+#ifdef ENCODER_TEST
+/*
+** The subroutines above are not tested by the usual test suite.  To test
+** these routines, compile just this one file with a -DENCODER_TEST=1 option
+** and run the result.
+*/
+int main(int argc, char **argv){
+  int i, j, n, m, nOut;
+  unsigned char in[30000];
+  unsigned char out[33000];
+
+  for(i=0; i<sizeof(in); i++){
+    printf("Test %d: ", i+1);
+    n = rand() % (i+1);
+    if( i%100==0 ){
+      int k;
+      for(j=k=0; j<n; j++){
+        /* if( k==0 || k=='\'' ) k++; */
+        in[j] = k;
+        k = (k+1)&0xff;
+      }
+    }else{
+      for(j=0; j<n; j++) in[j] = rand() & 0xff;
+    }
+    nOut = sqlite_encode_binary(in, n, out);
+    if( nOut!=strlen(out) ){
+      printf(" ERROR return value is %d instead of %d\n", nOut, strlen(out));
+      exit(1);
+    }
+    m = (256*n + 1262)/253;
+    printf("size %d->%d (max %d)", n, strlen(out)+1, m);
+    if( strlen(out)+1>m ){
+      printf(" ERROR output too big\n");
+      exit(1);
+    }
+    for(j=0; out[j]; j++){
+      if( out[j]=='\'' ){
+        printf(" ERROR contains (')\n");
+        exit(1);
+      }
+    }
+    j = sqlite_decode_binary(out, out);
+    if( j!=n ){
+      printf(" ERROR decode size %d\n", j);
+      exit(1);
+    }
+    if( memcmp(in, out, n)!=0 ){
+      printf(" ERROR decode mismatch\n");
+      exit(1);
+    }
+    printf(" OK\n");
+  }
+}
+#endif /* ENCODER_TEST */
-- 
cgit v1.2.3