Hello, the work is finished.
Version 4 of the patch is attached to this message.
- Add rough description of the algorithm as comment to
pg_utf8_increment() and pg_eucjp_increment().
- Fixed a bug of pg_utf8_increment() found while
working. pg_(utf8|eucjp)_increment are retested on whole valid
code points to be properly handled.
- The comment previously pointed out as being wrong in grammar
is left untouched. I'm sorry to bother you with my poor
English.
At Tue, 11 Oct 2011 16:55:00 +0900 (JST), Kyotaro HORIGUCHI
<horiguchi.kyot...@oss.ntt.co.jp> wrote
> > One thing I still think it would be useful to add,
> > though, is some comments to pg_utf8_increment() and
> > pg_eucjp_increment() describing the algorithm being used. Can you
> > take a crack at that?
>
> Yes I'll do it in a day or two.
Regards,
--
Kyotaro Horiguchi
NTT Open Source Software Center
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 8ceea82..59f8c37 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -5664,6 +5664,19 @@ pattern_selectivity(Const *patt, Pattern_Type ptype)
/*
+ * This function is "character increment" function for bytea used in
+ * make_greater_string() that has same interface with pg_wchar_tbl.charinc.
+ */
+static bool
+byte_increment(unsigned char *ptr, int len)
+{
+ if (*ptr >= 255) return false;
+
+ (*ptr)++;
+ return true;
+}
+
+/*
* Try to generate a string greater than the given string or any
* string it is a prefix of. If successful, return a palloc'd string
* in the form of a Const node; else return NULL.
@@ -5702,6 +5715,7 @@ make_greater_string(const Const *str_const, FmgrInfo *ltproc, Oid collation)
int len;
Datum cmpstr;
text *cmptxt = NULL;
+ character_incrementer charincfunc;
/*
* Get a modifiable copy of the prefix string in C-string format, and set
@@ -5763,29 +5777,33 @@ make_greater_string(const Const *str_const, FmgrInfo *ltproc, Oid collation)
}
}
+ if (datatype == BYTEAOID)
+ charincfunc = &byte_increment;
+ else
+ charincfunc = pg_database_encoding_character_incrementer();
+
while (len > 0)
{
- unsigned char *lastchar = (unsigned char *) (workstr + len - 1);
- unsigned char savelastchar = *lastchar;
+ int charlen = 1;
+ unsigned char *lastchar;
+ Const *workstr_const;
+
+ if (datatype != BYTEAOID)
+ charlen = len - pg_mbcliplen(workstr, len, len - 1);
+
+ lastchar = (unsigned char *) (workstr + len - charlen);
/*
- * Try to generate a larger string by incrementing the last byte.
+ * Try to generate a larger string by incrementing the last byte or
+ * character.
*/
- while (*lastchar < (unsigned char) 255)
- {
- Const *workstr_const;
-
- (*lastchar)++;
- if (datatype != BYTEAOID)
- {
- /* do not generate invalid encoding sequences */
- if (!pg_verifymbstr(workstr, len, true))
- continue;
- workstr_const = string_to_const(workstr, datatype);
- }
- else
+ if (charincfunc(lastchar, charlen))
+ {
+ if (datatype == BYTEAOID)
workstr_const = string_to_bytea_const(workstr, len);
+ else
+ workstr_const = string_to_const(workstr, datatype);
if (DatumGetBool(FunctionCall2Coll(ltproc,
collation,
@@ -5804,20 +5822,10 @@ make_greater_string(const Const *str_const, FmgrInfo *ltproc, Oid collation)
pfree(workstr_const);
}
- /* restore last byte so we don't confuse pg_mbcliplen */
- *lastchar = savelastchar;
-
/*
- * Truncate off the last character, which might be more than 1 byte,
- * depending on the character encoding.
+ * Truncate off the last character or byte.
*/
- if (datatype != BYTEAOID && pg_database_encoding_max_length() > 1)
- len = pg_mbcliplen(workstr, len, len - 1);
- else
- len -= 1;
-
- if (datatype != BYTEAOID)
- workstr[len] = '\0';
+ len -= charlen;
}
/* Failed... */
diff --git a/src/backend/utils/mb/wchar.c b/src/backend/utils/mb/wchar.c
index f23732f..a213636 100644
--- a/src/backend/utils/mb/wchar.c
+++ b/src/backend/utils/mb/wchar.c
@@ -1336,6 +1336,264 @@ pg_utf8_islegal(const unsigned char *source, int length)
/*
*-------------------------------------------------------------------
+ * character incrementer
+ *
+ * These functions accept "charptr", a pointer to the first byte of a
+ * maybe-multibyte character. Try `increment' the character and return
+ * true if successed. If these functions returns false, the character
+ * should be untouched. These functions must be implemented in
+ * correspondence with verifiers, in other words, the rewrited
+ * character by this function must pass the check by pg_*_verifier()
+ * if returns true.
+ * -------------------------------------------------------------------
+ */
+
+#ifndef FRONTEND
+static bool
+pg_generic_charinc(unsigned char *charptr, int len)
+{
+ unsigned char *lastchar = (unsigned char *) (charptr + len - 1);
+ unsigned char savelastchar = *lastchar;
+ const char *const_charptr = (const char *)charptr;
+
+ while (*lastchar < (unsigned char) 255)
+ {
+ (*lastchar)++;
+ if (!pg_verifymbstr(const_charptr, len, true))
+ continue;
+ return true;
+ }
+
+ *lastchar = savelastchar;
+ return false;
+}
+
+/*
+ * Calculate the valid UTF-8 byte sequence that is the smallest of the
+ * greater than the given valid UTF-8 byte sequence for single
+ * character. The word `valid' here means that pg_utf8_islegal() says
+ * that it is valid. pg_utf8_increment does this roughly with the
+ * following algorithm.
+ *
+ * - If the length of the sequence is 1, the byte is between 0x01 and
+ * 0x7f. It is simplly incremented if less than 0x7f.
+ *
+ * - Otherwise the bytes after the first one ranges between 0x80 and
+ * 0xbf. The sequence is incremented from the last byte and the
+ * carry is propagated up to the first byte.
+ *
+ * Only the UTF-8 byte sequences corresponding to the following
+ * unicode point which have no character allocated make this function
+ * to fail in spite of its validity.
+ *
+ * U+0007F, U+007FF, U+0FFFF, U+10FFFF
+ *
+ */
+static bool
+pg_utf8_increment(unsigned char *charptr, int length)
+{
+ unsigned char a;
+ unsigned char bak[4];
+ unsigned char limit;
+
+ switch (length)
+ {
+ default:
+ /* reject lengths 5 and 6 for now */
+ return false;
+ case 4:
+ bak[3] = charptr[3];
+ a = charptr[3];
+ if (a < 0xBF)
+ {
+ charptr[3]++;
+ break;
+ }
+ charptr[3] = 0x80;
+ /* FALL THRU */
+ case 3:
+ bak[2] = charptr[2];
+ a = charptr[2];
+ if (a < 0xBF)
+ {
+ charptr[2]++;
+ break;
+ }
+ charptr[2] = 0x80;
+ /* FALL THRU */
+ case 2:
+ bak[1] = charptr[1];
+ a = charptr[1];
+ switch (*charptr)
+ {
+ case 0xED:
+ limit = 0x9F;
+ break;
+
+ case 0xF4:
+ limit = 0x8F;
+ break;
+
+ default:
+ limit = 0xBF;
+
+ }
+
+ if (a < limit)
+ {
+ charptr[1]++;
+ break;
+ }
+
+ charptr[1] = 0x80;
+ /* FALL THRU */
+ case 1:
+ bak[0] = *charptr;
+ a = *charptr;
+ if (a == 0x7F || a == 0xDF || a == 0xEF || a == 0xF4)
+ {
+ /* Rewinding modified bytes and return fail. length is
+ * confirmed to be between 1 and 4 here. */
+ memcpy(charptr, bak, length);
+ return false;
+ }
+ charptr[0]++;
+ break;
+ }
+
+ return true;
+}
+
+/* Calculate the valid EUC-JP byte sequence that is the smallest of
+ * the greater than the given valid EUC-JP byte sequence for single
+ * character. The word `valid' here means that pg_eucjp_verifier()
+ * syas that it is valid. This function does this roughly with the
+ * following algorithm.
+ *
+ * - If the sequence starts with SS2(0x8e), it must be a two-byte
+ * sequence representing JIS X 0201 characters with the second byte
+ * ranges between 0xa1 and 0xde. It is simplly incremented at the
+ * second byte if less than 0xde, and otherwise rewrite whole the
+ * sequence to 0xa1 0xa1 as the result.
+ *
+ * - If the sequence starts with SS3(0x8f), it must be a three-byte
+ * sequence which the last two bytes ranges between 0xa1 and 0xfe.
+ * The bytes are incremented from the last within the range and
+ * propagate the carry up to the first byte.
+ *
+ * - If the sequence starts with the values other than the aboves and
+ * its MSB is set, it must be a two-byte sequence representing JIS
+ * X 0208 characters with both bytes ranges between 0xa1 and 0xfe.
+ * The bytes are incremented from the latter within the range and
+ * propagate the carry up to the first byte.
+ *
+ * - Otherwise the sequence is consists of single byte representing
+ * ASCII characters. It is incremented up to 0x7f.
+ *
+ * Only three EUC-JP byte sequences shown below which has no character
+ * allocated make this function to fail in spite of its validity.
+ *
+ * 0x7f, 0xfe 0xfe, 0x8f 0xfe 0xfe
+ *
+ */
+static bool
+pg_eucjp_increment(unsigned char *charptr, int length)
+{
+ unsigned char bak[3];
+ unsigned char c1, c2;
+ signed int i;
+
+ c1 = *charptr;
+
+ switch (c1)
+ {
+ case SS2: /* JIS X 0201 */
+ if (length != 2) return false;
+
+ c2 = charptr[1];
+
+ if (c2 > 0xde)
+ charptr[0] = charptr[1] = 0xa1;
+ else if (c2 < 0xa1)
+ charptr[1] = 0xa1;
+ else
+ charptr[1]++;
+
+ break;
+
+ case SS3: /* JIS X 0212 */
+ if (length != 3) return false;
+
+ for (i = 2 ; i > 0 ; i--)
+ {
+ bak[i] = charptr[i];
+ c2 = charptr[i];
+ if (c2 < 0xa1)
+ {
+ charptr[i] = 0xa1;
+ return true;
+ }
+ else if (c2 < 0xfe)
+ {
+ charptr[i]++;
+ break;
+ }
+ charptr[i] = 0xa1;
+ }
+
+
+ if (i == 0) /* Out of 3-byte code region */
+ {
+ charptr[1] = bak[1];
+ charptr[2] = bak[2];
+ return false;
+ }
+
+ break;
+
+ default:
+ if (IS_HIGHBIT_SET(c1)) /* JIS X 0208? */
+ {
+ if (length != 2) return false;
+
+ for (i = 1 ; i >= 0 ; i--) /* i must be signed */
+ {
+ bak[i] = charptr[i];
+ c2 = charptr[i];
+ if (c2 < 0xa1)
+ {
+ charptr[i] = 0xa1;
+ return true;
+ }
+ else if (c2 < 0xfe)
+ {
+ charptr[i]++;
+ break;
+ }
+ charptr[i] = 0xa1;
+ }
+
+ if (i < 0) /* Out of 2 byte code region */
+ {
+ charptr[0] = bak[0];
+ charptr[1] = bak[1];
+ return false;
+ }
+ }
+ else
+ { /* ASCII, single byte */
+ if (c1 > 0x7e)
+ return false;
+ (*charptr)++;
+ }
+ }
+
+ return true;
+}
+#endif
+
+/*
+ *-------------------------------------------------------------------
* encoding info table
* XXX must be sorted by the same order as enum pg_enc (in mb/pg_wchar.h)
*-------------------------------------------------------------------
@@ -1459,6 +1717,25 @@ pg_database_encoding_max_length(void)
}
/*
+ * give the character incrementer for the encoding for the current database
+ */
+character_incrementer
+pg_database_encoding_character_incrementer(void)
+{
+ switch (GetDatabaseEncoding())
+ {
+ case PG_UTF8:
+ return pg_utf8_increment;
+
+ case PG_EUC_JP:
+ return pg_eucjp_increment;
+
+ default:
+ return pg_generic_charinc;
+ }
+}
+
+/*
* Verify mbstr to make sure that it is validly encoded in the current
* database encoding. Otherwise same as pg_verify_mbstr().
*/
diff --git a/src/include/mb/pg_wchar.h b/src/include/mb/pg_wchar.h
index 826c7af..728175c 100644
--- a/src/include/mb/pg_wchar.h
+++ b/src/include/mb/pg_wchar.h
@@ -284,6 +284,8 @@ typedef int (*mblen_converter) (const unsigned char *mbstr);
typedef int (*mbdisplaylen_converter) (const unsigned char *mbstr);
+typedef bool (*character_incrementer) (unsigned char *mbstr, int len);
+
typedef int (*mbverifier) (const unsigned char *mbstr, int len);
typedef struct
@@ -389,6 +391,7 @@ extern int pg_encoding_mbcliplen(int encoding, const char *mbstr,
extern int pg_mbcharcliplen(const char *mbstr, int len, int imit);
extern int pg_encoding_max_length(int encoding);
extern int pg_database_encoding_max_length(void);
+extern character_incrementer pg_database_encoding_character_incrementer(void);
extern int PrepareClientEncoding(int encoding);
extern int SetClientEncoding(int encoding);
--
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