Updated sqlite_encode_binary() comments with tighter bounds on output length. (CVS...

FossilOrigin-Name: 826aab43d5967ece2a272c49ce62021fa4a2ceb3

diff --git a/manifest b/manifest
index 3b042fd2d507fb812264d81cfb81699ecbc90b3f..c0db1a90dda861b9d4115c52cc4c075733646802 100644 (file)
--- a/manifest
+++ b/manifest
@@ -1,5 +1,5 @@
-C Documented\sinteger\svalues\sused\sby\sPRAGMAs.\nFixed\smissing\send\stags\sin\sgenerated\sanchors.\s(CVS\s1022)
-D 2003-06-15T10:29:25
+C Updated\ssqlite_encode_binary()\scomments\swith\stighter\sbounds\son\soutput\slength.\s(CVS\s1023)
+D 2003-06-15T10:35:05
 F Makefile.in 9ad23ed4ca97f9670c4496432e3fbd4b3760ebde
 F Makefile.linux-gcc b86a99c493a5bfb402d1d9178dcdc4bd4b32f906
 F README f1de682fbbd94899d50aca13d387d1b3fd3be2dd
@@ -27,7 +27,7 @@ F src/btree_rb.c a0dd64f840417b13637160599bd2740c8a340366
 F src/build.c 936d10b33b326546280690bee7f20efaf19a6fe8
 F src/copy.c 9e47975ea96751c658bcf1a0c4f0bb7c6ee61e73
 F src/delete.c 0f81e6799c089487615d38e042a2de4d2d6192bc
-F src/encode.c ed720e54ec4ef4d4de651592f1dd1c74d422bbd2
+F src/encode.c a5fc03201e34b0015817202e9286bacf89e72048
 F src/expr.c ebdb0f3ee039c8030de25935ce2df030966540a6
 F src/func.c 33bbce6acaf9578ac99aa1f689968ccaf2ce43a2
 F src/hash.c 058f077c1f36f266581aa16f907a3903abf64aa3
@@ -165,7 +165,7 @@ F www/speed.tcl 296cc5632d069b56d3ef5409ca0df90f486c10fb
 F www/sqlite.tcl 4bd1729e320f5fa9125f0022b281fbe839192125
 F www/tclsqlite.tcl 1db15abeb446aad0caf0b95b8b9579720e4ea331
 F www/vdbe.tcl 14fdcc7fe8a60a6ba8584903636db8dc37eef26a
-P e13e8b05b4d146aa4ca9ed06e414e0c6a4fba4e4
-R 025a97aa1a8710d9abd04f450fb59b7a
+P 6c24dfbae56a16dd736de5297c1796818773df80
+R 58e24d713b97f4ba7b875ae8dce7497f
 U jplyon
-Z f0f06ece626e6fed7f80c90c5644e695
+Z fb46334e21926a895547abc49f262bff

diff --git a/manifest.uuid b/manifest.uuid
index 06d976ceae6b2592c6d88b7dc42f26b9cabca03b..617cb0330a523bef85ae3117cfd599ab8cc53458 100644 (file)
--- a/manifest.uuid
+++ b/manifest.uuid
@@ -1 +1 @@
-6c24dfbae56a16dd736de5297c1796818773df80
\ No newline at end of file
+826aab43d5967ece2a272c49ce62021fa4a2ceb3
\ No newline at end of file

diff --git a/src/encode.c b/src/encode.c
index b313d4f8210c22bdb66c4e37aa46ea608dfaaa93..b18564cb692049aa3d4a3dabc3e5db80c3c961d3 100644 (file)
--- a/src/encode.c
+++ b/src/encode.c
@@ -15,7 +15,7 @@
 ** 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 1.6 2003/05/10 03:36:54 drh Exp $
+** $Id: encode.c,v 1.7 2003/06/15 10:35:05 jplyon Exp $
 */
 #include <string.h>
 
@@ -44,7 +44,7 @@
 ** this.
 **
 ** To minimize the encoding size, we first add a fixed offset value to each 
-** byte in the sequence.  The addition is module 256.  (That is to say, if
+** 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
@@ -86,7 +86,7 @@
 **           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 to testing
+** 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
@@ -107,10 +107,10 @@
 ** string back into its original binary.
 **
 ** The result is written into a preallocated output buffer "out".
-** "out" must be able to hold at least (256*n + 1262)/253 bytes.
+** "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 253 bytes of input plus 2 bytes of fixed overhead.
-** (This is approximately 2 + 1.019*n or about a 2% size increase.)
+** 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.
@@ -159,7 +159,7 @@ int sqlite_encode_binary(const unsigned char *in, int n, unsigned char *out){
 
 /*
 ** Decode the string "in" into binary data and write it into "out".
-** This routine reverses the encoded created by sqlite_encode_binary().
+** 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.