Expose helper functions scan_quoted_identifier and scan_identifier.

Previously, this logic was embedded within SplitIdentifierString,
SplitDirectoriesString, and SplitGUCList. Factoring it out saves
a bit of duplicated code, and also makes it available to extensions
that might want to do similar things without necessarily wanting to
do exactly the same thing.

Reviewed-by: Matheus Alcantara <matheusssilv97@gmail.com>
Reviewed-by: Lukas Fittl <lukas@fittl.com>
Discussion: http://postgr.es/m/CA+Tgmob-0W8306mvrJX5Urtqt1AAasu8pi4yLrZ1XfwZU-Uj1w@mail.gmail.com

diff --git a/src/backend/utils/adt/varlena.c b/src/backend/utils/adt/varlena.c
index ecad6d6218401ddc460aa6957410fc1c122c8e63..c0ff51bd2fc16c2584228406f90f1a76af357751 100644 (file)
--- a/src/backend/utils/adt/varlena.c
+++ b/src/backend/utils/adt/varlena.c
@@ -2750,6 +2750,96 @@ textToQualifiedNameList(text *textval)
        return result;
 }
 
+/*
+ * scan_quoted_identifier - In-place scanner for quoted identifiers.
+ *
+ * *nextp should point to the opening double-quote character, and will be
+ * updated to point just past the end.  *endp is set to the position of
+ * the closing quote. The return value is the identifier, or NULL if the
+ * matching close-quote cannot be found.
+ *
+ * If we find two consecutive double quote characters, that doesn't end the
+ * identifier: instead, we collapse them into a double quote and include them
+ * in the resulting token. Note that this requires overwriting the rest of the
+ * string in place, including the portion beyond the final value of *nextp.
+ */
+char *
+scan_quoted_identifier(char **endp, char **nextp)
+{
+       char       *token = *nextp + 1;
+
+       for (;;)
+       {
+               *endp = strchr(*nextp + 1, '"');
+               if (*endp == NULL)
+                       return NULL;            /* mismatched quotes */
+               if ((*endp)[1] != '"')
+                       break;                          /* found end of quoted identifier */
+               /* Collapse adjacent quotes into one quote, and look again */
+               memmove(*endp, *endp + 1, strlen(*endp));
+               *nextp = *endp;
+       }
+       /* *endp now points at the terminating quote */
+       *nextp = *endp + 1;
+
+       return token;
+}
+
+/*
+ * scan_identifier - In-place scanner for quoted or unquoted identifiers.
+ *
+ * On success, *endp is set to the position where the caller should write '\0'
+ * to null-terminate the token, and *nextp is advanced past the token (and past
+ * the closing quote, if any).  The return value is the token content, or NULL
+ * if there is a syntax error (mismatched quotes or empty unquoted token).
+ *
+ * Unquoted identifiers are terminated by whitespace or the first occurrence
+ * of the separator character. Additionally, if downcase_unquoted = true,
+ * unquoted identifiers are downcased in place. See scan_quoted_identifier for
+ * an additional way in which we modify the string in place.
+ */
+char *
+scan_identifier(char **endp, char **nextp, char separator, bool downcase_unquoted)
+{
+       char       *token;
+
+       if (**nextp == '"')
+               return scan_quoted_identifier(endp, nextp);
+
+       /* Unquoted identifier --- extends to separator or whitespace */
+       token = *nextp;
+
+       while (**nextp && **nextp != separator && !scanner_isspace(**nextp))
+               (*nextp)++;
+
+       if (*nextp == token)
+               return NULL;                    /* empty token */
+
+       *endp = *nextp;
+
+       if (downcase_unquoted)
+       {
+               /*
+                * Downcase the identifier, using same code as main lexer does.
+                *
+                * XXX because we want to overwrite the input in-place, we cannot
+                * support a downcasing transformation that increases the string
+                * length.  This is not a problem given the current implementation of
+                * downcase_truncate_identifier, but we'll probably have to do
+                * something about this someday.
+                */
+               int                     len = *endp - token;
+               char       *downname = downcase_truncate_identifier(token, len, false);
+
+               Assert(strlen(downname) <= len);
+               strncpy(token, downname, len);  /* strncpy is required here */
+               pfree(downname);
+       }
+
+       return token;
+}
+
+
 /*
  * SplitIdentifierString --- parse a string containing identifiers
  *
@@ -2794,53 +2884,9 @@ SplitIdentifierString(char *rawstring, char separator,
                char       *curname;
                char       *endp;
 
-               if (*nextp == '"')
-               {
-                       /* Quoted name --- collapse quote-quote pairs, no downcasing */
-                       curname = nextp + 1;
-                       for (;;)
-                       {
-                               endp = strchr(nextp + 1, '"');
-                               if (endp == NULL)
-                                       return false;   /* mismatched quotes */
-                               if (endp[1] != '"')
-                                       break;          /* found end of quoted name */
-                               /* Collapse adjacent quotes into one quote, and look again */
-                               memmove(endp, endp + 1, strlen(endp));
-                               nextp = endp;
-                       }
-                       /* endp now points at the terminating quote */
-                       nextp = endp + 1;
-               }
-               else
-               {
-                       /* Unquoted name --- extends to separator or whitespace */
-                       char       *downname;
-                       int                     len;
-
-                       curname = nextp;
-                       while (*nextp && *nextp != separator &&
-                                  !scanner_isspace(*nextp))
-                               nextp++;
-                       endp = nextp;
-                       if (curname == nextp)
-                               return false;   /* empty unquoted name not allowed */
-
-                       /*
-                        * Downcase the identifier, using same code as main lexer does.
-                        *
-                        * XXX because we want to overwrite the input in-place, we cannot
-                        * support a downcasing transformation that increases the string
-                        * length.  This is not a problem given the current implementation
-                        * of downcase_truncate_identifier, but we'll probably have to do
-                        * something about this someday.
-                        */
-                       len = endp - curname;
-                       downname = downcase_truncate_identifier(curname, len, false);
-                       Assert(strlen(downname) <= len);
-                       strncpy(curname, downname, len);        /* strncpy is required here */
-                       pfree(downname);
-               }
+               curname = scan_identifier(&endp, &nextp, separator, true);
+               if (curname == NULL)
+                       return false;           /* mismatched quotes or empty name */
 
                while (scanner_isspace(*nextp))
                        nextp++;                        /* skip trailing whitespace */
@@ -2924,20 +2970,9 @@ SplitDirectoriesString(char *rawstring, char separator,
                if (*nextp == '"')
                {
                        /* Quoted name --- collapse quote-quote pairs */
-                       curname = nextp + 1;
-                       for (;;)
-                       {
-                               endp = strchr(nextp + 1, '"');
-                               if (endp == NULL)
-                                       return false;   /* mismatched quotes */
-                               if (endp[1] != '"')
-                                       break;          /* found end of quoted name */
-                               /* Collapse adjacent quotes into one quote, and look again */
-                               memmove(endp, endp + 1, strlen(endp));
-                               nextp = endp;
-                       }
-                       /* endp now points at the terminating quote */
-                       nextp = endp + 1;
+                       curname = scan_quoted_identifier(&endp, &nextp);
+                       if (curname == NULL)
+                               return false;   /* mismatched quotes */
                }
                else
                {
@@ -3042,35 +3077,9 @@ SplitGUCList(char *rawstring, char separator,
                char       *curname;
                char       *endp;
 
-               if (*nextp == '"')
-               {
-                       /* Quoted name --- collapse quote-quote pairs */
-                       curname = nextp + 1;
-                       for (;;)
-                       {
-                               endp = strchr(nextp + 1, '"');
-                               if (endp == NULL)
-                                       return false;   /* mismatched quotes */
-                               if (endp[1] != '"')
-                                       break;          /* found end of quoted name */
-                               /* Collapse adjacent quotes into one quote, and look again */
-                               memmove(endp, endp + 1, strlen(endp));
-                               nextp = endp;
-                       }
-                       /* endp now points at the terminating quote */
-                       nextp = endp + 1;
-               }
-               else
-               {
-                       /* Unquoted name --- extends to separator or whitespace */
-                       curname = nextp;
-                       while (*nextp && *nextp != separator &&
-                                  !scanner_isspace(*nextp))
-                               nextp++;
-                       endp = nextp;
-                       if (curname == nextp)
-                               return false;   /* empty unquoted name not allowed */
-               }
+               curname = scan_identifier(&endp, &nextp, separator, false);
+               if (curname == NULL)
+                       return false;           /* mismatched quotes or empty name */
 
                while (scanner_isspace(*nextp))
                        nextp++;                        /* skip trailing whitespace */

diff --git a/src/include/utils/varlena.h b/src/include/utils/varlena.h
index 4b32574a075f700e93da580f2cb28e49d2f4e2f9..fe8d8a5895291e487b52177655d24cfb4ccf6ea4 100644 (file)
--- a/src/include/utils/varlena.h
+++ b/src/include/utils/varlena.h
@@ -27,6 +27,9 @@ extern int    varstr_levenshtein_less_equal(const char *source, int slen,
                                                                                  int ins_c, int del_c, int sub_c,
                                                                                  int max_d, bool trusted);
 extern List *textToQualifiedNameList(text *textval);
+extern char *scan_quoted_identifier(char **endp, char **nextp);
+extern char *scan_identifier(char **endp, char **nextp, char separator,
+                                                        bool downcase_unquoted);
 extern bool SplitIdentifierString(char *rawstring, char separator,
                                                                  List **namelist);
 extern bool SplitDirectoriesString(char *rawstring, char separator,