Cosmetic changes for jsonpath_gram.y and jsonpath_scan.l
authorAlexander Korotkov <akorotkov@postgresql.org>
Mon, 25 Mar 2019 12:42:51 +0000 (15:42 +0300)
committerAlexander Korotkov <akorotkov@postgresql.org>
Mon, 25 Mar 2019 12:42:51 +0000 (15:42 +0300)
This commit include formatting improvements, renamings and comments.  Also,
it makes jsonpath_scan.l be more uniform with other our lexers.  Firstly,
states names are renamed to more short alternatives.  Secondly, <INITIAL>
prefix removed from the rules.  Corresponding rules are moved to the tail, so
they would anyway work only in initial state.

Author: Alexander Korotkov
Reviewed-by: John Naylor
src/backend/utils/adt/jsonpath_gram.y
src/backend/utils/adt/jsonpath_scan.l

index 47ebb2a0e09ad439ddea8abecefb66a631644b55..76155963fc61e7374b65e421a5265aab03186270 100644 (file)
@@ -4,6 +4,8 @@
  * jsonpath_gram.y
  *  Grammar definitions for jsonpath datatype
  *
+ * Transforms tokenized jsonpath into tree of JsonPathParseItem structs.
+ *
  * Copyright (c) 2019, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
@@ -37,15 +39,17 @@ int jsonpath_yylex(union YYSTYPE *yylval_param);
 int    jsonpath_yyparse(JsonPathParseResult **result);
 void jsonpath_yyerror(JsonPathParseResult **result, const char *message);
 
-static JsonPathParseItem *makeItemType(int type);
+static JsonPathParseItem *makeItemType(JsonPathItemType type);
 static JsonPathParseItem *makeItemString(JsonPathString *s);
 static JsonPathParseItem *makeItemVariable(JsonPathString *s);
 static JsonPathParseItem *makeItemKey(JsonPathString *s);
 static JsonPathParseItem *makeItemNumeric(JsonPathString *s);
 static JsonPathParseItem *makeItemBool(bool val);
-static JsonPathParseItem *makeItemBinary(int type, JsonPathParseItem *la,
+static JsonPathParseItem *makeItemBinary(JsonPathItemType type,
+                                        JsonPathParseItem *la,
                                         JsonPathParseItem *ra);
-static JsonPathParseItem *makeItemUnary(int type, JsonPathParseItem *a);
+static JsonPathParseItem *makeItemUnary(JsonPathItemType type,
+                                       JsonPathParseItem *a);
 static JsonPathParseItem *makeItemList(List *list);
 static JsonPathParseItem *makeIndexArray(List *list);
 static JsonPathParseItem *makeAny(int first, int last);
@@ -75,9 +79,9 @@ static JsonPathParseItem *makeItemLikeRegex(JsonPathParseItem *expr,
 
 %union {
    JsonPathString      str;
-   List                *elems;     /* list of JsonPathParseItem */
-   List                *indexs;    /* list of integers */
-   JsonPathParseItem   *value;
+   List               *elems;  /* list of JsonPathParseItem */
+   List               *indexs; /* list of integers */
+   JsonPathParseItem  *value;
    JsonPathParseResult *result;
    JsonPathItemType    optype;
    bool                boolean;
@@ -160,7 +164,7 @@ comp_op:
    ;
 
 delimited_predicate:
-   '(' predicate ')'                       { $$ = $2; }
+   '(' predicate ')'               { $$ = $2; }
    | EXISTS_P '(' expr ')'         { $$ = makeItemUnary(jpiExists, $3); }
    ;
 
@@ -170,9 +174,10 @@ predicate:
    | predicate AND_P predicate     { $$ = makeItemBinary(jpiAnd, $1, $3); }
    | predicate OR_P predicate      { $$ = makeItemBinary(jpiOr, $1, $3); }
    | NOT_P delimited_predicate     { $$ = makeItemUnary(jpiNot, $2); }
-   | '(' predicate ')' IS_P UNKNOWN_P  { $$ = makeItemUnary(jpiIsUnknown, $2); }
+   | '(' predicate ')' IS_P UNKNOWN_P
+                                   { $$ = makeItemUnary(jpiIsUnknown, $2); }
    | expr STARTS_P WITH_P starts_with_initial
-       { $$ = makeItemBinary(jpiStartsWith, $1, $4); }
+                                   { $$ = makeItemBinary(jpiStartsWith, $1, $4); }
    | expr LIKE_REGEX_P STRING_P    { $$ = makeItemLikeRegex($1, &$3, NULL); }
    | expr LIKE_REGEX_P STRING_P FLAG_P STRING_P
                                    { $$ = makeItemLikeRegex($1, &$3, &$5); }
@@ -232,7 +237,8 @@ any_level:
 any_path:
    ANY_P                           { $$ = makeAny(0, -1); }
    | ANY_P '{' any_level '}'       { $$ = makeAny($3, $3); }
-   | ANY_P '{' any_level TO_P any_level '}'    { $$ = makeAny($3, $5); }
+   | ANY_P '{' any_level TO_P any_level '}'
+                                   { $$ = makeAny($3, $5); }
    ;
 
 accessor_op:
@@ -285,10 +291,15 @@ method:
    ;
 %%
 
-static JsonPathParseItem*
-makeItemType(int type)
+/*
+ * The helper functions below allocate and fill JsonPathParseItem's of various
+ * types.
+ */
+
+static JsonPathParseItem *
+makeItemType(JsonPathItemType type)
 {
-   JsonPathParseItemv = palloc(sizeof(*v));
+   JsonPathParseItem  *v = palloc(sizeof(*v));
 
    CHECK_FOR_INTERRUPTS();
 
@@ -298,10 +309,10 @@ makeItemType(int type)
    return v;
 }
 
-static JsonPathParseItem*
+static JsonPathParseItem *
 makeItemString(JsonPathString *s)
 {
-   JsonPathParseItem *v;
+   JsonPathParseItem  *v;
 
    if (s == NULL)
    {
@@ -320,7 +331,7 @@ makeItemString(JsonPathString *s)
 static JsonPathParseItem *
 makeItemVariable(JsonPathString *s)
 {
-   JsonPathParseItem *v;
+   JsonPathParseItem  *v;
 
    v = makeItemType(jpiVariable);
    v->value.string.val = s->val;
@@ -332,7 +343,7 @@ makeItemVariable(JsonPathString *s)
 static JsonPathParseItem *
 makeItemKey(JsonPathString *s)
 {
-   JsonPathParseItem *v;
+   JsonPathParseItem  *v;
 
    v = makeItemString(s);
    v->type = jpiKey;
@@ -343,7 +354,7 @@ makeItemKey(JsonPathString *s)
 static JsonPathParseItem *
 makeItemNumeric(JsonPathString *s)
 {
-   JsonPathParseItem       *v;
+   JsonPathParseItem  *v;
 
    v = makeItemType(jpiNumeric);
    v->value.numeric =
@@ -356,7 +367,7 @@ makeItemNumeric(JsonPathString *s)
 static JsonPathParseItem *
 makeItemBool(bool val)
 {
-   JsonPathParseItem *v = makeItemType(jpiBool);
+   JsonPathParseItem  *v = makeItemType(jpiBool);
 
    v->value.boolean = val;
 
@@ -364,7 +375,7 @@ makeItemBool(bool val)
 }
 
 static JsonPathParseItem *
-makeItemBinary(int type, JsonPathParseItem* la, JsonPathParseItem *ra)
+makeItemBinary(JsonPathItemType type, JsonPathParseItem *la, JsonPathParseItem *ra)
 {
    JsonPathParseItem  *v = makeItemType(type);
 
@@ -375,7 +386,7 @@ makeItemBinary(int type, JsonPathParseItem* la, JsonPathParseItem *ra)
 }
 
 static JsonPathParseItem *
-makeItemUnary(int type, JsonPathParseItem* a)
+makeItemUnary(JsonPathItemType type, JsonPathParseItem *a)
 {
    JsonPathParseItem  *v;
 
@@ -401,8 +412,9 @@ makeItemUnary(int type, JsonPathParseItem* a)
 static JsonPathParseItem *
 makeItemList(List *list)
 {
-   JsonPathParseItem *head, *end;
-   ListCell   *cell = list_head(list);
+   JsonPathParseItem  *head,
+                      *end;
+   ListCell           *cell = list_head(list);
 
    head = end = (JsonPathParseItem *) lfirst(cell);
 
@@ -427,8 +439,8 @@ makeItemList(List *list)
 static JsonPathParseItem *
 makeIndexArray(List *list)
 {
-   JsonPathParseItem   *v = makeItemType(jpiIndexArray);
-   ListCell            *cell;
+   JsonPathParseItem  *v = makeItemType(jpiIndexArray);
+   ListCell           *cell;
    int                 i = 0;
 
    Assert(list_length(list) > 0);
@@ -439,7 +451,7 @@ makeIndexArray(List *list)
 
    foreach(cell, list)
    {
-       JsonPathParseItem *jpi = lfirst(cell);
+       JsonPathParseItem  *jpi = lfirst(cell);
 
        Assert(jpi->type == jpiSubscript);
 
@@ -453,7 +465,7 @@ makeIndexArray(List *list)
 static JsonPathParseItem *
 makeAny(int first, int last)
 {
-   JsonPathParseItem *v = makeItemType(jpiAny);
+   JsonPathParseItem  *v = makeItemType(jpiAny);
 
    v->value.anybounds.first = (first >= 0) ? first : PG_UINT32_MAX;
    v->value.anybounds.last = (last >= 0) ? last : PG_UINT32_MAX;
@@ -465,9 +477,9 @@ static JsonPathParseItem *
 makeItemLikeRegex(JsonPathParseItem *expr, JsonPathString *pattern,
                  JsonPathString *flags)
 {
-   JsonPathParseItem *v = makeItemType(jpiLikeRegex);
-   int         i;
-   int         cflags = REG_ADVANCED;
+   JsonPathParseItem  *v = makeItemType(jpiLikeRegex);
+   int                 i;
+   int                 cflags = REG_ADVANCED;
 
    v->value.like_regex.expr = expr;
    v->value.like_regex.pattern = pattern->val;
@@ -510,4 +522,12 @@ makeItemLikeRegex(JsonPathParseItem *expr, JsonPathString *pattern,
    return v;
 }
 
+/*
+ * jsonpath_scan.l is compiled as part of jsonpath_gram.y.  Currently, this is
+ * unavoidable because jsonpath_gram does not create a .h file to export its
+ * token symbols.  If these files ever grow large enough to be worth compiling
+ * separately, that could be fixed; but for now it seems like useless
+ * complication.
+ */
+
 #include "jsonpath_scan.c"
index 02cb54ee7f927d676c091f46c7521709a068101d..e93307f4073f657e4d89bd070a7c394d1f68f2b1 100644 (file)
@@ -4,6 +4,9 @@
  * jsonpath_scan.l
  * Lexical parser for jsonpath datatype
  *
+ * Splits jsonpath string into tokens represented as JsonPathString structs.
+ * Decodes unicode and hex escaped strings.
+ *
  * Copyright (c) 2019, PostgreSQL Global Development Group
  *
  * IDENTIFICATION
@@ -19,9 +22,6 @@
 
 static JsonPathString scanstring;
 
-/* No reason to constrain amount of data slurped */
-/* #define YY_READ_BUF_SIZE 16777216 */
-
 /* Handles to the buffer that the lexer uses internally */
 static YY_BUFFER_STATE scanbufhandle;
 static char *scanbuf;
@@ -29,9 +29,7 @@ static int    scanbuflen;
 
 static void addstring(bool init, char *s, int l);
 static void addchar(bool init, char s);
-static int checkSpecialVal(void); /* examine scanstring for the special
-                                  * value */
-
+static enum yytokentype checkKeyword(void);
 static void parseUnicode(char *s, int l);
 static void parseHexChars(char *s, int l);
 
@@ -60,11 +58,22 @@ fprintf_to_ereport(const char *fmt, const char *msg)
 %option noyyrealloc
 %option noyyfree
 
-%x xQUOTED
-%x xNONQUOTED
-%x xVARQUOTED
-%x xSINGLEQUOTED
-%x xCOMMENT
+/*
+ * We use exclusive states for quoted, signle-quoted and non-quoted strings,
+ * quoted variable names and C-tyle comments.
+ * Exclusive states:
+ *  <xq> - quoted strings
+ *  <xnq> - non-quoted strings
+ *  <xvq> - quoted variable names
+ *  <xsq> - single-quoted strings
+ *  <xc> - C-style comment
+ */
+
+%x xq
+%x xnq
+%x xvq
+%x xsq
+%x xc
 
 special         [\?\%\$\.\[\]\{\}\(\)\|\&\!\=\<\>\@\#\,\*:\-\+\/]
 any            [^\?\%\$\.\[\]\{\}\(\)\|\&\!\=\<\>\@\#\,\*:\-\+\/\\\"\' \t\n\r\f]
@@ -73,189 +82,188 @@ hex_dig       [0-9A-Fa-f]
 unicode        \\u({hex_dig}{4}|\{{hex_dig}{1,6}\})
 hex_char   \\x{hex_dig}{2}
 
-
 %%
 
-<INITIAL>\&\&                  { return AND_P; }
-
-<INITIAL>\|\|                  { return OR_P; }
-
-<INITIAL>\!                        { return NOT_P; }
-
-<INITIAL>\*\*                  { return ANY_P; }
-
-<INITIAL>\<                        { return LESS_P; }
-
-<INITIAL>\<\=                  { return LESSEQUAL_P; }
-
-<INITIAL>\=\=                  { return EQUAL_P; }
-
-<INITIAL>\<\>                  { return NOTEQUAL_P; }
+<xnq>{any}+                        {
+                                   addstring(false, yytext, yyleng);
+                               }
 
-<INITIAL>\!\=                  { return NOTEQUAL_P; }
+<xnq>{blank}+                  {
+                                   yylval->str = scanstring;
+                                   BEGIN INITIAL;
+                                   return checkKeyword();
+                               }
 
-<INITIAL>\>\=                  { return GREATEREQUAL_P; }
 
-<INITIAL>\>                        { return GREATER_P; }
+<xnq>\/\*                      {
+                                   yylval->str = scanstring;
+                                   BEGIN xc;
+                               }
 
-<INITIAL>\${any}+              {
-                                   addstring(true, yytext + 1, yyleng - 1);
-                                   addchar(false, '\0');
+<xnq>({special}|\"|\')         {
                                    yylval->str = scanstring;
-                                   return VARIABLE_P;
+                                   yyless(0);
+                                   BEGIN INITIAL;
+                                   return checkKeyword();
                                }
 
-<INITIAL>\$\"                  {
-                                   addchar(true, '\0');
-                                   BEGIN xVARQUOTED;
+<xnq><<EOF>>                   {
+                                   yylval->str = scanstring;
+                                   BEGIN INITIAL;
+                                   return checkKeyword();
                                }
 
-<INITIAL>{special}             { return *yytext; }
+<xnq,xq,xvq,xsq>\\[\"\'\\]     { addchar(false, yytext[1]); }
 
-<INITIAL>{blank}+              { /* ignore */ }
+<xnq,xq,xvq,xsq>\\b                { addchar(false, '\b'); }
 
-<INITIAL>\/\*                  {
-                                   addchar(true, '\0');
-                                   BEGIN xCOMMENT;
-                               }
+<xnq,xq,xvq,xsq>\\f                { addchar(false, '\f'); }
 
-<INITIAL>[0-9]+(\.[0-9]+)?[eE][+-]?[0-9]+  /* float */  {
-                                   addstring(true, yytext, yyleng);
-                                   addchar(false, '\0');
-                                   yylval->str = scanstring;
-                                   return NUMERIC_P;
-                               }
+<xnq,xq,xvq,xsq>\\n                { addchar(false, '\n'); }
 
-<INITIAL>\.[0-9]+[eE][+-]?[0-9]+  /* float */  {
-                                   addstring(true, yytext, yyleng);
-                                   addchar(false, '\0');
-                                   yylval->str = scanstring;
-                                   return NUMERIC_P;
-                               }
+<xnq,xq,xvq,xsq>\\r                { addchar(false, '\r'); }
 
-<INITIAL>([0-9]+)?\.[0-9]+     {
-                                   addstring(true, yytext, yyleng);
-                                   addchar(false, '\0');
-                                   yylval->str = scanstring;
-                                   return NUMERIC_P;
-                               }
+<xnq,xq,xvq,xsq>\\t                { addchar(false, '\t'); }
 
-<INITIAL>[0-9]+                    {
-                                   addstring(true, yytext, yyleng);
-                                   addchar(false, '\0');
-                                   yylval->str = scanstring;
-                                   return INT_P;
-                               }
+<xnq,xq,xvq,xsq>\\v                { addchar(false, '\v'); }
 
-<INITIAL>{any}+                    {
-                                   addstring(true, yytext, yyleng);
-                                   BEGIN xNONQUOTED;
-                               }
+<xnq,xq,xvq,xsq>{unicode}+     { parseUnicode(yytext, yyleng); }
 
-<INITIAL>\"                        {
-                                   addchar(true, '\0');
-                                   BEGIN xQUOTED;
-                               }
+<xnq,xq,xvq,xsq>{hex_char}+        { parseHexChars(yytext, yyleng); }
 
-<INITIAL>\'                        {
-                                   addchar(true, '\0');
-                                   BEGIN xSINGLEQUOTED;
-                               }
+<xnq,xq,xvq,xsq>\\x                { yyerror(NULL, "Hex character sequence is invalid"); }
 
-<INITIAL>\\                        {
-                                   yyless(0);
-                                   addchar(true, '\0');
-                                   BEGIN xNONQUOTED;
-                               }
+<xnq,xq,xvq,xsq>\\u                { yyerror(NULL, "Unicode sequence is invalid"); }
 
-<xNONQUOTED>{any}+             {
-                                   addstring(false, yytext, yyleng);
-                               }
+<xnq,xq,xvq,xsq>\\.                { yyerror(NULL, "Escape sequence is invalid"); }
 
-<xNONQUOTED>{blank}+           {
-                                   yylval->str = scanstring;
-                                   BEGIN INITIAL;
-                                   return checkSpecialVal();
-                               }
+<xnq,xq,xvq,xsq>\\             { yyerror(NULL, "Unexpected end after backslash"); }
 
+<xq,xvq,xsq><<EOF>>                { yyerror(NULL, "Unexpected end of quoted string"); }
 
-<xNONQUOTED>\/\*               {
+<xq>\"                         {
                                    yylval->str = scanstring;
-                                   BEGIN xCOMMENT;
+                                   BEGIN INITIAL;
+                                   return STRING_P;
                                }
 
-<xNONQUOTED>({special}|\"|\')  {
+<xvq>\"                            {
                                    yylval->str = scanstring;
-                                   yyless(0);
                                    BEGIN INITIAL;
-                                   return checkSpecialVal();
+                                   return VARIABLE_P;
                                }
 
-<xNONQUOTED><<EOF>>                {
+<xsq>\'                            {
                                    yylval->str = scanstring;
                                    BEGIN INITIAL;
-                                   return checkSpecialVal();
+                                   return STRING_P;
                                }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\[\"\'\\]    { addchar(false, yytext[1]); }
+<xq,xvq>[^\\\"]+               { addstring(false, yytext, yyleng); }
+
+<xsq>[^\\\']+                  { addstring(false, yytext, yyleng); }
+
+<xc>\*\/                       { BEGIN INITIAL; }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\b   { addchar(false, '\b'); }
+<xc>[^\*]+                     { }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\f   { addchar(false, '\f'); }
+<xc>\*                         { }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\n   { addchar(false, '\n'); }
+<xc><<EOF>>                        { yyerror(NULL, "Unexpected end of comment"); }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\r   { addchar(false, '\r'); }
+\&\&                           { return AND_P; }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\t   { addchar(false, '\t'); }
+\|\|                           { return OR_P; }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\v   { addchar(false, '\v'); }
+\!                             { return NOT_P; }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>{unicode}+        { parseUnicode(yytext, yyleng); }
+\*\*                           { return ANY_P; }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>{hex_char}+   { parseHexChars(yytext, yyleng); }
+\<                             { return LESS_P; }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\x   { yyerror(NULL, "Hex character sequence is invalid"); }
+\<\=                           { return LESSEQUAL_P; }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\u   { yyerror(NULL, "Unicode sequence is invalid"); }
+\=\=                           { return EQUAL_P; }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\.   { yyerror(NULL, "Escape sequence is invalid"); }
+\<\>                           { return NOTEQUAL_P; }
 
-<xNONQUOTED,xQUOTED,xVARQUOTED,xSINGLEQUOTED>\\        { yyerror(NULL, "Unexpected end after backslash"); }
+\!\=                           { return NOTEQUAL_P; }
 
-<xQUOTED,xVARQUOTED,xSINGLEQUOTED><<EOF>>          { yyerror(NULL, "Unexpected end of quoted string"); }
+\>\=                           { return GREATEREQUAL_P; }
 
-<xQUOTED>\"                        {
+\>                             { return GREATER_P; }
+
+\${any}+                       {
+                                   addstring(true, yytext + 1, yyleng - 1);
+                                   addchar(false, '\0');
                                    yylval->str = scanstring;
-                                   BEGIN INITIAL;
-                                   return STRING_P;
+                                   return VARIABLE_P;
+                               }
+
+\$\"                           {
+                                   addchar(true, '\0');
+                                   BEGIN xvq;
                                }
 
-<xVARQUOTED>\"                 {
+{special}                      { return *yytext; }
+
+{blank}+                       { /* ignore */ }
+
+\/\*                           {
+                                   addchar(true, '\0');
+                                   BEGIN xc;
+                               }
+
+[0-9]+(\.[0-9]+)?[eE][+-]?[0-9]+ { /* float */
+                                   addstring(true, yytext, yyleng);
+                                   addchar(false, '\0');
                                    yylval->str = scanstring;
-                                   BEGIN INITIAL;
-                                   return VARIABLE_P;
+                                   return NUMERIC_P;
                                }
 
-<xSINGLEQUOTED>\'              {
+\.[0-9]+[eE][+-]?[0-9]+            { /* float */
+                                   addstring(true, yytext, yyleng);
+                                   addchar(false, '\0');
                                    yylval->str = scanstring;
-                                   BEGIN INITIAL;
-                                   return STRING_P;
+                                   return NUMERIC_P;
                                }
 
-<xQUOTED,xVARQUOTED>[^\\\"]+   { addstring(false, yytext, yyleng); }
+([0-9]+)?\.[0-9]+              {
+                                   addstring(true, yytext, yyleng);
+                                   addchar(false, '\0');
+                                   yylval->str = scanstring;
+                                   return NUMERIC_P;
+                               }
 
-<xSINGLEQUOTED>[^\\\']+            { addstring(false, yytext, yyleng); }
+[0-9]+                         {
+                                   addstring(true, yytext, yyleng);
+                                   addchar(false, '\0');
+                                   yylval->str = scanstring;
+                                   return INT_P;
+                               }
 
-<INITIAL><<EOF>>               { yyterminate(); }
+{any}+                         {
+                                   addstring(true, yytext, yyleng);
+                                   BEGIN xnq;
+                               }
 
-<xCOMMENT>\*\/                 { BEGIN INITIAL; }
+\"                             {
+                                   addchar(true, '\0');
+                                   BEGIN xq;
+                               }
 
-<xCOMMENT>[^\*]+               { }
+\'                             {
+                                   addchar(true, '\0');
+                                   BEGIN xsq;
+                               }
 
-<xCOMMENT>\*                   { }
+\\                             {
+                                   yyless(0);
+                                   addchar(true, '\0');
+                                   BEGIN xnq;
+                               }
 
-<xCOMMENT><<EOF>>              { yyerror(NULL, "Unexpected end of comment"); }
+<<EOF>>                            { yyterminate(); }
 
 %%
 
@@ -292,7 +300,6 @@ typedef struct JsonPathKeyword
  * Array of key words should be sorted by length and then
  * alphabetical order
  */
-
 static const JsonPathKeyword keywords[] = {
    { 2, false, IS_P,       "is"},
    { 2, false, TO_P,       "to"},
@@ -317,8 +324,9 @@ static const JsonPathKeyword keywords[] = {
    { 10,false, LIKE_REGEX_P, "like_regex"},
 };
 
-static int
-checkSpecialVal()
+/* Check if current scanstring value is a keyword */
+static enum yytokentype
+checkKeyword()
 {
    int                     res = IDENT_P;
    int                     diff;
@@ -329,7 +337,7 @@ checkSpecialVal()
    if (scanstring.len > keywords[lengthof(keywords) - 1].len)
        return res;
 
-   while(StopLow < StopHigh)
+   while (StopLow < StopHigh)
    {
        StopMiddle = StopLow + ((StopHigh - StopLow) >> 1);
 
@@ -397,49 +405,50 @@ jsonpath_scanner_finish(void)
    pfree(scanbuf);
 }
 
+/*
+ * Resize scanstring so that it can append string of given length.
+ * Reinitialize if required.
+ */
 static void
-addstring(bool init, char *s, int l)
+resizeString(bool init, int appendLen)
 {
    if (init)
    {
-       scanstring.total = 32;
-       scanstring.val = palloc(scanstring.total);
+       scanstring.total = Max(32, appendLen);
+       scanstring.val = (char *) palloc(scanstring.total);
        scanstring.len = 0;
    }
-
-   if (s && l)
+   else
    {
-       while(scanstring.len + l + 1 >= scanstring.total)
+       if (scanstring.len + appendLen >= scanstring.total)
        {
-           scanstring.total *= 2;
+           while (scanstring.len + appendLen >= scanstring.total)
+               scanstring.total *= 2;
            scanstring.val = repalloc(scanstring.val, scanstring.total);
        }
-
-       memcpy(scanstring.val + scanstring.len, s, l);
-       scanstring.len += l;
    }
 }
 
+/* Add set of bytes at "s" of length "l" to scanstring */
 static void
-addchar(bool init, char s)
+addstring(bool init, char *s, int l)
 {
-   if (init)
-   {
-       scanstring.total = 32;
-       scanstring.val = palloc(scanstring.total);
-       scanstring.len = 0;
-   }
-   else if(scanstring.len + 1 >= scanstring.total)
-   {
-       scanstring.total *= 2;
-       scanstring.val = repalloc(scanstring.val, scanstring.total);
-   }
+   resizeString(init, l + 1);
+   memcpy(scanstring.val + scanstring.len, s, l);
+   scanstring.len += l;
+}
 
-   scanstring.val[ scanstring.len ] = s;
-   if (s != '\0')
+/* Add single byte "c" to scanstring */
+static void
+addchar(bool init, char c)
+{
+   resizeString(init, 1);
+   scanstring.val[scanstring.len] = c;
+   if (c != '\0')
        scanstring.len++;
 }
 
+/* Interface to jsonpath parser */
 JsonPathParseResult *
 parsejsonpath(const char *str, int len)
 {
@@ -447,7 +456,7 @@ parsejsonpath(const char *str, int len)
 
    jsonpath_scanner_init(str, len);
 
-   if (jsonpath_yyparse((void*)&parseresult) != 0)
+   if (jsonpath_yyparse((void *) &parseresult) != 0)
        jsonpath_yyerror(NULL, "bugus input");
 
    jsonpath_scanner_finish();
@@ -455,6 +464,7 @@ parsejsonpath(const char *str, int len)
    return parseresult;
 }
 
+/* Turn hex character into integer */
 static int
 hexval(char c)
 {
@@ -468,6 +478,7 @@ hexval(char c)
    return 0; /* not reached */
 }
 
+/* Add given unicode character to scanstring */
 static void
 addUnicodeChar(int ch)
 {
@@ -515,6 +526,7 @@ addUnicodeChar(int ch)
    }
 }
 
+/* Add unicode character and process its hi surrogate */
 static void
 addUnicode(int ch, int *hi_surrogate)
 {
@@ -592,6 +604,7 @@ parseUnicode(char *s, int l)
    }
 }
 
+/* Parse sequence of hex-encoded characters */
 static void
 parseHexChars(char *s, int l)
 {
@@ -601,7 +614,8 @@ parseHexChars(char *s, int l)
 
    for (i = 0; i < l / 4; i++)
    {
-       int         ch = (hexval(s[i * 4 + 2]) << 4) | hexval(s[i * 4 + 3]);
+       int         ch = (hexval(s[i * 4 + 2]) << 4) |
+                         hexval(s[i * 4 + 3]);
 
        addUnicodeChar(ch);
    }