Remove jsonapi.c's lex_accept().

At first glance, this function seems useful, but it actually increases
the amount of code required rather than decreasing it. Inline the
logic into the callers instead; most callers don't use the 'lexeme'
argument for anything and as a result considerable simplification is
possible.

Along the way, fix the header comment for the nearby function
lex_expect(), which mislabeled it as lex_accept().

Patch by me, reviewed by David Steele, Mark Dilger, and Andrew
Dunstan.

Discussion: http://postgr.es/m/CA+TgmoYfOXhd27MUDGioVh6QtpD0C1K-f6ObSA10AWiHBAL5bA@mail.gmail.com

diff --git a/src/backend/utils/adt/jsonapi.c b/src/backend/utils/adt/jsonapi.c
index fc8af9f861ebe3e9e67141596fb07186d776269b..9e14306b6f6202b25b4acf147f62ae6622be4984 100644 (file)
--- a/src/backend/utils/adt/jsonapi.c
+++ b/src/backend/utils/adt/jsonapi.c
@@ -69,44 +69,7 @@ lex_peek(JsonLexContext *lex)
 }
 
 /*
- * lex_accept
- *
- * accept the look_ahead token and move the lexer to the next token if the
- * look_ahead token matches the token parameter. In that case, and if required,
- * also hand back the de-escaped lexeme.
- *
- * returns true if the token matched, false otherwise.
- */
-static inline bool
-lex_accept(JsonLexContext *lex, JsonTokenType token, char **lexeme)
-{
-   if (lex->token_type == token)
-   {
-       if (lexeme != NULL)
-       {
-           if (lex->token_type == JSON_TOKEN_STRING)
-           {
-               if (lex->strval != NULL)
-                   *lexeme = pstrdup(lex->strval->data);
-           }
-           else
-           {
-               int         len = (lex->token_terminator - lex->token_start);
-               char       *tokstr = palloc(len + 1);
-
-               memcpy(tokstr, lex->token_start, len);
-               tokstr[len] = '\0';
-               *lexeme = tokstr;
-           }
-       }
-       json_lex(lex);
-       return true;
-   }
-   return false;
-}
-
-/*
- * lex_accept
+ * lex_expect
  *
  * move the lexer to the next token if the current look_ahead token matches
  * the parameter token. Otherwise, report an error.
@@ -114,7 +77,9 @@ lex_accept(JsonLexContext *lex, JsonTokenType token, char **lexeme)
 static inline void
 lex_expect(JsonParseContext ctx, JsonLexContext *lex, JsonTokenType token)
 {
-   if (!lex_accept(lex, token, NULL))
+   if (lex_peek(lex) == token)
+       json_lex(lex);
+   else
        report_parse_error(ctx, lex);
 }
 
@@ -260,12 +225,14 @@ json_count_array_elements(JsonLexContext *lex)
    lex_expect(JSON_PARSE_ARRAY_START, &copylex, JSON_TOKEN_ARRAY_START);
    if (lex_peek(&copylex) != JSON_TOKEN_ARRAY_END)
    {
-       do
+       while (1)
        {
            count++;
            parse_array_element(&copylex, &nullSemAction);
+           if (copylex.token_type != JSON_TOKEN_COMMA)
+               break;
+           json_lex(&copylex);
        }
-       while (lex_accept(&copylex, JSON_TOKEN_COMMA, NULL));
    }
    lex_expect(JSON_PARSE_ARRAY_NEXT, &copylex, JSON_TOKEN_ARRAY_END);
 
@@ -286,35 +253,41 @@ parse_scalar(JsonLexContext *lex, JsonSemAction *sem)
 {
    char       *val = NULL;
    json_scalar_action sfunc = sem->scalar;
-   char      **valaddr;
    JsonTokenType tok = lex_peek(lex);
 
-   valaddr = sfunc == NULL ? NULL : &val;
-
    /* a scalar must be a string, a number, true, false, or null */
-   switch (tok)
+   if (tok != JSON_TOKEN_STRING && tok != JSON_TOKEN_NUMBER &&
+       tok != JSON_TOKEN_TRUE && tok != JSON_TOKEN_FALSE &&
+       tok != JSON_TOKEN_NULL)
+       report_parse_error(JSON_PARSE_VALUE, lex);
+
+   /* if no semantic function, just consume the token */
+   if (sfunc == NULL)
    {
-       case JSON_TOKEN_TRUE:
-           lex_accept(lex, JSON_TOKEN_TRUE, valaddr);
-           break;
-       case JSON_TOKEN_FALSE:
-           lex_accept(lex, JSON_TOKEN_FALSE, valaddr);
-           break;
-       case JSON_TOKEN_NULL:
-           lex_accept(lex, JSON_TOKEN_NULL, valaddr);
-           break;
-       case JSON_TOKEN_NUMBER:
-           lex_accept(lex, JSON_TOKEN_NUMBER, valaddr);
-           break;
-       case JSON_TOKEN_STRING:
-           lex_accept(lex, JSON_TOKEN_STRING, valaddr);
-           break;
-       default:
-           report_parse_error(JSON_PARSE_VALUE, lex);
+       json_lex(lex);
+       return;
+   }
+
+   /* extract the de-escaped string value, or the raw lexeme */
+   if (lex_peek(lex) == JSON_TOKEN_STRING)
+   {
+       if (lex->strval != NULL)
+           val = pstrdup(lex->strval->data);
+   }
+   else
+   {
+       int         len = (lex->token_terminator - lex->token_start);
+
+       val = palloc(len + 1);
+       memcpy(val, lex->token_start, len);
+       val[len] = '\0';
    }
 
-   if (sfunc != NULL)
-       (*sfunc) (sem->semstate, val, tok);
+   /* consume the token */
+   json_lex(lex);
+
+   /* invoke the callback */
+   (*sfunc) (sem->semstate, val, tok);
 }
 
 static void
@@ -330,14 +303,13 @@ parse_object_field(JsonLexContext *lex, JsonSemAction *sem)
    json_ofield_action ostart = sem->object_field_start;
    json_ofield_action oend = sem->object_field_end;
    bool        isnull;
-   char      **fnameaddr = NULL;
    JsonTokenType tok;
 
-   if (ostart != NULL || oend != NULL)
-       fnameaddr = &fname;
-
-   if (!lex_accept(lex, JSON_TOKEN_STRING, fnameaddr))
+   if (lex_peek(lex) != JSON_TOKEN_STRING)
        report_parse_error(JSON_PARSE_STRING, lex);
+   if ((ostart != NULL || oend != NULL) && lex->strval != NULL)
+       fname = pstrdup(lex->strval->data);
+   json_lex(lex);
 
    lex_expect(JSON_PARSE_OBJECT_LABEL, lex, JSON_TOKEN_COLON);
 
@@ -387,16 +359,19 @@ parse_object(JsonLexContext *lex, JsonSemAction *sem)
     */
    lex->lex_level++;
 
-   /* we know this will succeed, just clearing the token */
-   lex_expect(JSON_PARSE_OBJECT_START, lex, JSON_TOKEN_OBJECT_START);
+   Assert(lex_peek(lex) == JSON_TOKEN_OBJECT_START);
+   json_lex(lex);
 
    tok = lex_peek(lex);
    switch (tok)
    {
        case JSON_TOKEN_STRING:
            parse_object_field(lex, sem);
-           while (lex_accept(lex, JSON_TOKEN_COMMA, NULL))
+           while (lex_peek(lex) == JSON_TOKEN_COMMA)
+           {
+               json_lex(lex);
                parse_object_field(lex, sem);
+           }
            break;
        case JSON_TOKEN_OBJECT_END:
            break;
@@ -473,8 +448,11 @@ parse_array(JsonLexContext *lex, JsonSemAction *sem)
 
        parse_array_element(lex, sem);
 
-       while (lex_accept(lex, JSON_TOKEN_COMMA, NULL))
+       while (lex_peek(lex) == JSON_TOKEN_COMMA)
+       {
+           json_lex(lex);
            parse_array_element(lex, sem);
+       }
    }
 
    lex_expect(JSON_PARSE_ARRAY_NEXT, lex, JSON_TOKEN_ARRAY_END);