1 files changed, 246 insertions, 0 deletions
diff --git a/jsonpath.c b/jsonpath.c
new file mode 100644
index 0000000..8de8327
--- /dev/null
+++ b/jsonpath.c
@@ -0,0 +1,246 @@
+#include "jsonpath.h"
+
+#include <ctype.h>
+
+/* NB: These macros evaluate their argument multiple times. */
+
+#define isletter(c) (((c) >= 'A' && (c) <= 'Z') || ((c) >= 'a' && (c) <= 'z'))
+	/* isalpha() is locale-specific.  This simply matches [A-Za-z] . */
+#define isextended(c) ((unsigned char)(c) > 127)
+
+/* Note that Unicode characters are allowed in identifiers. */
+#define identifier_start(c) (isletter(c) || (c) == '_' || (c) == '$' || isextended(c))
+#define identifier_char(c) (identifier_start(c) || isdigit(c))
+
+#define integer_start(c) (isdigit(c) || (c) == '+' || (c) == '-')
+
+/*
+ * Note that skip_spaces differs from skip_whitespace in json.c
+ * in that this function treats '\f' and '\v' as whitespace.
+ * This is because JSON does not accept these characters as
+ * whitespace, but since this is JSONPath,
+ * we can do whatever we want here :-)
+ */
+static void skip_spaces(const char **sp)
+{
+	const char *s = *sp;
+	while (isspace(*s))
+		s++;
+	*sp = s;
+}
+
+static jp_element *mkElement(jp_element_type type, bool rd)
+{
+	jp_element *elem = palloc0(sizeof(*elem));
+	elem->type = type;
+	elem->recursive_descent = rd;
+	return elem;
+}
+
+static jp_element *mkRoot(void)
+{
+	jp_element *elem = mkElement(JP_ROOT, false);
+	return elem;
+}
+
+static jp_element *mkWildcard(bool rd)
+{
+	jp_element *elem = mkElement(JP_WILDCARD, rd);
+	return elem;
+}
+
+static jp_element *mkIndexSubscript(int index, bool rd)
+{
+	jp_element *elem = mkElement(JP_INDEX_SUBSCRIPT, rd);
+	elem->data.index = index;
+	return elem;
+}
+
+static jp_element *mkKeySubscript(char *key, size_t length, bool rd)
+{
+	jp_element *elem = mkElement(JP_KEY_SUBSCRIPT, rd);
+	elem->data.key.ptr = key;
+	elem->data.key.length = length;
+	return elem;
+}
+
+char *jp_show(JSONPath *jp)
+{
+	StringInfoData	string[1];
+	ListCell		*cell;
+	jp_element		*elem;
+	bool			rd;
+	char			*tmp;
+
+	initStringInfo(string);
+
+	foreach(cell, jp) {
+		elem = lfirst(cell);
+		rd   = elem->recursive_descent;
+
+		switch (elem->type) {
+			case JP_ROOT:
+				appendStringInfoChar(string, '$');
+				break;
+			case JP_WILDCARD:
+				appendStringInfoString(string, rd ? "..[*]" : "[*]");
+				break;
+			case JP_INDEX_SUBSCRIPT:
+				appendStringInfo(string, "%s[%ld]", rd ? ".." : "", elem->data.index);
+				break;
+			case JP_KEY_SUBSCRIPT:
+				tmp = json_encode_string(elem->data.key.ptr, elem->data.key.length, '"');
+				Assert(tmp != NULL);
+				appendStringInfo(string, "%s[%s]", rd ? ".." : "", tmp);
+				pfree(tmp);
+				break;
+			default:
+				Assert(false);
+		}
+	}
+
+	return string->data;
+}
+
+JSONPath *jp_parse(const char *pattern)
+{
+	JSONPath	*jp					= NIL;
+	const char	*s					= pattern;
+	const char	*p;
+	bool		recursive_descent 	= false;
+	bool		bracket				= false;
+	const char	*err_msg			= NULL;
+	long		index;
+	char		*key;
+	size_t		key_length;
+	
+	skip_spaces(&s);
+	
+	/* pattern may not be empty */
+	if (!*s)
+		return NULL;
+	
+	jp = lappend(jp, mkRoot());
+	
+	if (*s == '$') {
+		s++;
+		goto begin_element;
+	} else if (*s != '.') {
+		goto dot_subscript; // implicit '.' at beginning
+	}
+	
+begin_element:
+	skip_spaces(&s);
+
+	recursive_descent = false;
+	bracket = false;
+
+	if (*s == '\0')
+		goto end;
+	if (s[0] == '.' && s[1] == '.') {
+		recursive_descent = true;
+		s += 2;
+		goto dot_subscript;
+	}
+	if (s[0] == '.') {
+		s++;
+		goto dot_subscript;
+	}
+	if (s[0] == '[') {
+		s++;
+		goto bracket_subscript;
+	}
+
+	goto failed;
+
+next_element:
+	if (bracket) {
+		skip_spaces(&s);
+		if (*s != ']')
+			goto failed;
+		s++;
+	}
+	goto begin_element;
+
+dot_subscript:
+	skip_spaces(&s);
+	
+	if (*s == '*')
+		goto wildcard;
+	if (integer_start(*s))
+		goto integer;
+	if (identifier_start(*s))
+		goto identifier;
+	if (*s == '"' || *s == '\'')
+		goto string;
+	if (*s == '[') {
+		s++;
+		goto bracket_subscript;
+	}
+
+	goto failed;
+
+bracket_subscript:
+	skip_spaces(&s);
+
+	bracket = true;
+
+	if (*s == '*')
+		goto wildcard;
+	if (integer_start(*s))
+		goto integer;
+	if (identifier_start(*s)) {
+		err_msg = "Identifiers may not be bracketed.  This syntax is reserved for future use.";
+		goto failed;
+	}
+	if (*s == '"' || *s == '\'')
+		goto string;
+	
+	goto failed;
+
+wildcard:
+	s++;
+	jp = lappend(jp, mkWildcard(recursive_descent));
+	goto next_element;
+
+integer:
+	p = s;
+	errno = 0;
+	index = strtol(s, (char**)&p, 10);
+	if (p <= s || errno != 0)
+		goto failed;
+	s = p;
+	
+	jp = lappend(jp, mkIndexSubscript(index, recursive_descent));
+	goto next_element;
+
+identifier:
+	p = s;
+	while (identifier_char(*p))
+		p++;
+	key = pnstrdup(s, p - s);
+	key_length = p - s;
+	s = p;
+
+	jp = lappend(jp, mkKeySubscript(key, key_length, recursive_descent));
+	goto next_element;
+
+string:
+	key = json_decode_string(&s, &key_length, false);
+	if (!key)
+		goto failed;
+	
+	jp = lappend(jp, mkKeySubscript(key, key_length, recursive_descent));
+	goto next_element;
+
+end:
+	return jp;
+
+failed:
+	return NULL;
+}
+
+List *jp_match(JSONPath *jp, json_node *json)
+{
+	
+}