Adding upstream version 5.7.1.upstream/5.7.1

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1362 insertions, 0 deletions

diff --git a/contrib/ccan/json/json.c b/contrib/ccan/json/json.c
new file mode 100644
index 0000000..a86c4db
--- /dev/null
+++ b/contrib/ccan/json/json.c
@@ -0,0 +1,1362 @@
+/* SPDX-License-Identifier: MIT
+ * Source: https://ccodearchive.net/info/json.html
+ * Copyright (C) 2011 Joseph A. Adams (joeyadams3.14159@gmail.com) */
+
+#include "json.h"
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#define out_of_memory() do {                    \
+		fprintf(stderr, "Out of memory.\n");    \
+		exit(EXIT_FAILURE);                     \
+	} while (0)
+
+/* Sadly, strdup is not portable. */
+static char *json_strdup(const char *str)
+{
+	char *ret = (char*) malloc(strlen(str) + 1);
+	if (ret == NULL)
+		out_of_memory();
+	strcpy(ret, str);
+	return ret;
+}
+
+/* String buffer */
+
+typedef struct
+{
+	char *cur;
+	char *end;
+	char *start;
+} SB;
+
+static void sb_init(SB *sb)
+{
+	sb->start = (char*) malloc(17);
+	if (sb->start == NULL)
+		out_of_memory();
+	sb->cur = sb->start;
+	sb->end = sb->start + 16;
+}
+
+/* sb and need may be evaluated multiple times. */
+#define sb_need(sb, need) do {                  \
+		if ((sb)->end - (sb)->cur < (need))     \
+			sb_grow(sb, need);                  \
+	} while (0)
+
+static void sb_grow(SB *sb, int need)
+{
+	size_t length = sb->cur - sb->start;
+	size_t alloc = sb->end - sb->start;
+	
+	do {
+		alloc *= 2;
+	} while (alloc < length + need);
+	
+	sb->start = (char*) realloc(sb->start, alloc + 1);
+	if (sb->start == NULL)
+		out_of_memory();
+	sb->cur = sb->start + length;
+	sb->end = sb->start + alloc;
+}
+
+static void sb_put(SB *sb, const char *bytes, int count)
+{
+	sb_need(sb, count);
+	memcpy(sb->cur, bytes, count);
+	sb->cur += count;
+}
+
+#define sb_putc(sb, c) do {         \
+		if ((sb)->cur >= (sb)->end) \
+			sb_grow(sb, 1);         \
+		*(sb)->cur++ = (c);         \
+	} while (0)
+
+static void sb_puts(SB *sb, const char *str)
+{
+	sb_put(sb, str, strlen(str));
+}
+
+static char *sb_finish(SB *sb)
+{
+	*sb->cur = 0;
+	assert(sb->start <= sb->cur && strlen(sb->start) == (size_t)(sb->cur - sb->start));
+	return sb->start;
+}
+
+static void sb_free(SB *sb)
+{
+	free(sb->start);
+}
+
+/*
+ * Unicode helper functions
+ *
+ * These are taken from the ccan/charset module and customized a bit.
+ * Putting them here means the compiler can (choose to) inline them,
+ * and it keeps ccan/json from having a dependency.
+ */
+
+/*
+ * Type for Unicode codepoints.
+ * We need our own because wchar_t might be 16 bits.
+ */
+typedef uint32_t uchar_t;
+
+/*
+ * Validate a single UTF-8 character starting at @s.
+ * The string must be null-terminated.
+ *
+ * If it's valid, return its length (1 thru 4).
+ * If it's invalid or clipped, return 0.
+ *
+ * This function implements the syntax given in RFC3629, which is
+ * the same as that given in The Unicode Standard, Version 6.0.
+ *
+ * It has the following properties:
+ *
+ *  * All codepoints U+0000..U+10FFFF may be encoded,
+ *    except for U+D800..U+DFFF, which are reserved
+ *    for UTF-16 surrogate pair encoding.
+ *  * UTF-8 byte sequences longer than 4 bytes are not permitted,
+ *    as they exceed the range of Unicode.
+ *  * The sixty-six Unicode "non-characters" are permitted
+ *    (namely, U+FDD0..U+FDEF, U+xxFFFE, and U+xxFFFF).
+ */
+static int utf8_validate_cz(const char *s)
+{
+	unsigned char c = *s++;
+	
+	if (c <= 0x7F) {        /* 00..7F */
+		return 1;
+	} else if (c <= 0xC1) { /* 80..C1 */
+		/* Disallow overlong 2-byte sequence. */
+		return 0;
+	} else if (c <= 0xDF) { /* C2..DF */
+		/* Make sure subsequent byte is in the range 0x80..0xBF. */
+		if (((unsigned char)*s++ & 0xC0) != 0x80)
+			return 0;
+		
+		return 2;
+	} else if (c <= 0xEF) { /* E0..EF */
+		/* Disallow overlong 3-byte sequence. */
+		if (c == 0xE0 && (unsigned char)*s < 0xA0)
+			return 0;
+		
+		/* Disallow U+D800..U+DFFF. */
+		if (c == 0xED && (unsigned char)*s > 0x9F)
+			return 0;
+		
+		/* Make sure subsequent bytes are in the range 0x80..0xBF. */
+		if (((unsigned char)*s++ & 0xC0) != 0x80)
+			return 0;
+		if (((unsigned char)*s++ & 0xC0) != 0x80)
+			return 0;
+		
+		return 3;
+	} else if (c <= 0xF4) { /* F0..F4 */
+		/* Disallow overlong 4-byte sequence. */
+		if (c == 0xF0 && (unsigned char)*s < 0x90)
+			return 0;
+		
+		/* Disallow codepoints beyond U+10FFFF. */
+		if (c == 0xF4 && (unsigned char)*s > 0x8F)
+			return 0;
+		
+		/* Make sure subsequent bytes are in the range 0x80..0xBF. */
+		if (((unsigned char)*s++ & 0xC0) != 0x80)
+			return 0;
+		if (((unsigned char)*s++ & 0xC0) != 0x80)
+			return 0;
+		if (((unsigned char)*s++ & 0xC0) != 0x80)
+			return 0;
+		
+		return 4;
+	} else {                /* F5..FF */
+		return 0;
+	}
+}
+
+/* Validate a null-terminated UTF-8 string. */
+static bool utf8_validate(const char *s)
+{
+	int len;
+	
+	for (; *s != 0; s += len) {
+		len = utf8_validate_cz(s);
+		if (len == 0)
+			return false;
+	}
+	
+	return true;
+}
+
+/*
+ * Read a single UTF-8 character starting at @s,
+ * returning the length, in bytes, of the character read.
+ *
+ * This function assumes input is valid UTF-8,
+ * and that there are enough characters in front of @s.
+ */
+static int utf8_read_char(const char *s, uchar_t *out)
+{
+	const unsigned char *c = (const unsigned char*) s;
+	
+	assert(utf8_validate_cz(s));
+
+	if (c[0] <= 0x7F) {
+		/* 00..7F */
+		*out = c[0];
+		return 1;
+	} else if (c[0] <= 0xDF) {
+		/* C2..DF (unless input is invalid) */
+		*out = ((uchar_t)c[0] & 0x1F) << 6 |
+		       ((uchar_t)c[1] & 0x3F);
+		return 2;
+	} else if (c[0] <= 0xEF) {
+		/* E0..EF */
+		*out = ((uchar_t)c[0] &  0xF) << 12 |
+		       ((uchar_t)c[1] & 0x3F) << 6  |
+		       ((uchar_t)c[2] & 0x3F);
+		return 3;
+	} else {
+		/* F0..F4 (unless input is invalid) */
+		*out = ((uchar_t)c[0] &  0x7) << 18 |
+		       ((uchar_t)c[1] & 0x3F) << 12 |
+		       ((uchar_t)c[2] & 0x3F) << 6  |
+		       ((uchar_t)c[3] & 0x3F);
+		return 4;
+	}
+}
+
+/*
+ * Write a single UTF-8 character to @s,
+ * returning the length, in bytes, of the character written.
+ *
+ * @unicode must be U+0000..U+10FFFF, but not U+D800..U+DFFF.
+ *
+ * This function will write up to 4 bytes to @out.
+ */
+static int utf8_write_char(uchar_t unicode, char *out)
+{
+	unsigned char *o = (unsigned char*) out;
+	
+	assert(unicode <= 0x10FFFF && !(unicode >= 0xD800 && unicode <= 0xDFFF));
+
+	if (unicode <= 0x7F) {
+		/* U+0000..U+007F */
+		*o++ = unicode;
+		return 1;
+	} else if (unicode <= 0x7FF) {
+		/* U+0080..U+07FF */
+		*o++ = 0xC0 | unicode >> 6;
+		*o++ = 0x80 | (unicode & 0x3F);
+		return 2;
+	} else if (unicode <= 0xFFFF) {
+		/* U+0800..U+FFFF */
+		*o++ = 0xE0 | unicode >> 12;
+		*o++ = 0x80 | (unicode >> 6 & 0x3F);
+		*o++ = 0x80 | (unicode & 0x3F);
+		return 3;
+	} else {
+		/* U+10000..U+10FFFF */
+		*o++ = 0xF0 | unicode >> 18;
+		*o++ = 0x80 | (unicode >> 12 & 0x3F);
+		*o++ = 0x80 | (unicode >> 6 & 0x3F);
+		*o++ = 0x80 | (unicode & 0x3F);
+		return 4;
+	}
+}
+
+/*
+ * Compute the Unicode codepoint of a UTF-16 surrogate pair.
+ *
+ * @uc should be 0xD800..0xDBFF, and @lc should be 0xDC00..0xDFFF.
+ * If they aren't, this function returns false.
+ */
+static bool from_surrogate_pair(uint16_t uc, uint16_t lc, uchar_t *unicode)
+{
+	if (uc >= 0xD800 && uc <= 0xDBFF && lc >= 0xDC00 && lc <= 0xDFFF) {
+		*unicode = 0x10000 + ((((uchar_t)uc & 0x3FF) << 10) | (lc & 0x3FF));
+		return true;
+	} else {
+		return false;
+	}
+}
+
+/*
+ * Construct a UTF-16 surrogate pair given a Unicode codepoint.
+ *
+ * @unicode must be U+10000..U+10FFFF.
+ */
+static void to_surrogate_pair(uchar_t unicode, uint16_t *uc, uint16_t *lc)
+{
+	uchar_t n;
+	
+	assert(unicode >= 0x10000 && unicode <= 0x10FFFF);
+	
+	n = unicode - 0x10000;
+	*uc = ((n >> 10) & 0x3FF) | 0xD800;
+	*lc = (n & 0x3FF) | 0xDC00;
+}
+
+#define is_space(c) ((c) == '\t' || (c) == '\n' || (c) == '\r' || (c) == ' ')
+#define is_digit(c) ((c) >= '0' && (c) <= '9')
+
+static bool parse_value     (const char **sp, JsonNode        **out);
+static bool parse_string    (const char **sp, char            **out);
+static bool parse_number    (const char **sp, double           *out);
+static bool parse_array     (const char **sp, JsonNode        **out);
+static bool parse_object    (const char **sp, JsonNode        **out);
+static bool parse_hex16     (const char **sp, uint16_t         *out);
+
+static bool expect_literal  (const char **sp, const char *str);
+static void skip_space      (const char **sp);
+
+static void emit_value              (SB *out, const JsonNode *node);
+static void emit_value_indented     (SB *out, const JsonNode *node, const char *space, int indent_level);
+static void emit_string             (SB *out, const char *str);
+static void emit_number             (SB *out, double num);
+static void emit_array              (SB *out, const JsonNode *array);
+static void emit_array_indented     (SB *out, const JsonNode *array, const char *space, int indent_level);
+static void emit_object             (SB *out, const JsonNode *object);
+static void emit_object_indented    (SB *out, const JsonNode *object, const char *space, int indent_level);
+
+static int write_hex16(char *out, uint16_t val);
+
+static JsonNode *mknode(JsonTag tag);
+static void append_node(JsonNode *parent, JsonNode *child);
+static void prepend_node(JsonNode *parent, JsonNode *child);
+static void append_member(JsonNode *object, char *key, JsonNode *value);
+
+/* Assertion-friendly validity checks */
+static bool tag_is_valid(unsigned int tag);
+static bool number_is_valid(const char *num);
+
+JsonNode *json_decode(const char *json)
+{
+	const char *s = json;
+	JsonNode *ret;
+	
+	skip_space(&s);
+	if (!parse_value(&s, &ret))
+		return NULL;
+	
+	skip_space(&s);
+	if (*s != 0) {
+		json_delete(ret);
+		return NULL;
+	}
+	
+	return ret;
+}
+
+char *json_encode(const JsonNode *node)
+{
+	return json_stringify(node, NULL);
+}
+
+char *json_encode_string(const char *str)
+{
+	SB sb;
+	sb_init(&sb);
+	
+	emit_string(&sb, str);
+	
+	return sb_finish(&sb);
+}
+
+char *json_stringify(const JsonNode *node, const char *space)
+{
+	SB sb;
+	sb_init(&sb);
+	
+	if (space != NULL)
+		emit_value_indented(&sb, node, space, 0);
+	else
+		emit_value(&sb, node);
+	
+	return sb_finish(&sb);
+}
+
+void json_delete(JsonNode *node)
+{
+	if (node != NULL) {
+		json_remove_from_parent(node);
+		
+		switch (node->tag) {
+			case JSON_STRING:
+				free(node->string_);
+				break;
+			case JSON_ARRAY:
+			case JSON_OBJECT:
+			{
+				JsonNode *child, *next;
+				for (child = node->children.head; child != NULL; child = next) {
+					next = child->next;
+					json_delete(child);
+				}
+				break;
+			}
+			default:;
+		}
+		
+		free(node);
+	}
+}
+
+bool json_validate(const char *json)
+{
+	const char *s = json;
+	
+	skip_space(&s);
+	if (!parse_value(&s, NULL))
+		return false;
+	
+	skip_space(&s);
+	if (*s != 0)
+		return false;
+	
+	return true;
+}
+
+JsonNode *json_find_element(JsonNode *array, int index)
+{
+	JsonNode *element;
+	int i = 0;
+	
+	if (array == NULL || array->tag != JSON_ARRAY)
+		return NULL;
+	
+	json_foreach(element, array) {
+		if (i == index)
+			return element;
+		i++;
+	}
+	
+	return NULL;
+}
+
+JsonNode *json_find_member(JsonNode *object, const char *name)
+{
+	JsonNode *member;
+	
+	if (object == NULL || object->tag != JSON_OBJECT)
+		return NULL;
+	
+	json_foreach(member, object)
+		if (strcmp(member->key, name) == 0)
+			return member;
+	
+	return NULL;
+}
+
+JsonNode *json_first_child(const JsonNode *node)
+{
+	if (node != NULL && (node->tag == JSON_ARRAY || node->tag == JSON_OBJECT))
+		return node->children.head;
+	return NULL;
+}
+
+static JsonNode *mknode(JsonTag tag)
+{
+	JsonNode *ret = (JsonNode*) calloc(1, sizeof(JsonNode));
+	if (ret == NULL)
+		out_of_memory();
+	ret->tag = tag;
+	return ret;
+}
+
+JsonNode *json_mknull(void)
+{
+	return mknode(JSON_NULL);
+}
+
+JsonNode *json_mkbool(bool b)
+{
+	JsonNode *ret = mknode(JSON_BOOL);
+	ret->bool_ = b;
+	return ret;
+}
+
+static JsonNode *mkstring(char *s)
+{
+	JsonNode *ret = mknode(JSON_STRING);
+	ret->string_ = s;
+	return ret;
+}
+
+JsonNode *json_mkstring(const char *s)
+{
+	return mkstring(json_strdup(s));
+}
+
+JsonNode *json_mknumber(double n)
+{
+	JsonNode *node = mknode(JSON_NUMBER);
+	node->number_ = n;
+	return node;
+}
+
+JsonNode *json_mkarray(void)
+{
+	return mknode(JSON_ARRAY);
+}
+
+JsonNode *json_mkobject(void)
+{
+	return mknode(JSON_OBJECT);
+}
+
+static void append_node(JsonNode *parent, JsonNode *child)
+{
+	child->parent = parent;
+	child->prev = parent->children.tail;
+	child->next = NULL;
+	
+	if (parent->children.tail != NULL)
+		parent->children.tail->next = child;
+	else
+		parent->children.head = child;
+	parent->children.tail = child;
+}
+
+static void prepend_node(JsonNode *parent, JsonNode *child)
+{
+	child->parent = parent;
+	child->prev = NULL;
+	child->next = parent->children.head;
+	
+	if (parent->children.head != NULL)
+		parent->children.head->prev = child;
+	else
+		parent->children.tail = child;
+	parent->children.head = child;
+}
+
+static void append_member(JsonNode *object, char *key, JsonNode *value)
+{
+	value->key = key;
+	append_node(object, value);
+}
+
+void json_append_element(JsonNode *array, JsonNode *element)
+{
+	assert(array->tag == JSON_ARRAY);
+	assert(element->parent == NULL);
+	
+	append_node(array, element);
+}
+
+void json_prepend_element(JsonNode *array, JsonNode *element)
+{
+	assert(array->tag == JSON_ARRAY);
+	assert(element->parent == NULL);
+	
+	prepend_node(array, element);
+}
+
+void json_append_member(JsonNode *object, const char *key, JsonNode *value)
+{
+	assert(object->tag == JSON_OBJECT);
+	assert(value->parent == NULL);
+	
+	append_member(object, json_strdup(key), value);
+}
+
+void json_prepend_member(JsonNode *object, const char *key, JsonNode *value)
+{
+	assert(object->tag == JSON_OBJECT);
+	assert(value->parent == NULL);
+	
+	value->key = json_strdup(key);
+	prepend_node(object, value);
+}
+
+void json_remove_from_parent(JsonNode *node)
+{
+	JsonNode *parent = node->parent;
+	
+	if (parent != NULL) {
+		if (node->prev != NULL)
+			node->prev->next = node->next;
+		else
+			parent->children.head = node->next;
+		if (node->next != NULL)
+			node->next->prev = node->prev;
+		else
+			parent->children.tail = node->prev;
+		
+		free(node->key);
+		
+		node->parent = NULL;
+		node->prev = node->next = NULL;
+		node->key = NULL;
+	}
+}
+
+static bool parse_value(const char **sp, JsonNode **out)
+{
+	const char *s = *sp;
+	
+	switch (*s) {
+		case 'n':
+			if (expect_literal(&s, "null")) {
+				if (out)
+					*out = json_mknull();
+				*sp = s;
+				return true;
+			}
+			return false;
+		
+		case 'f':
+			if (expect_literal(&s, "false")) {
+				if (out)
+					*out = json_mkbool(false);
+				*sp = s;
+				return true;
+			}
+			return false;
+		
+		case 't':
+			if (expect_literal(&s, "true")) {
+				if (out)
+					*out = json_mkbool(true);
+				*sp = s;
+				return true;
+			}
+			return false;
+		
+		case '"': {
+			char *str;
+			if (parse_string(&s, out ? &str : NULL)) {
+				if (out)
+					*out = mkstring(str);
+				*sp = s;
+				return true;
+			}
+			return false;
+		}
+		
+		case '[':
+			if (parse_array(&s, out)) {
+				*sp = s;
+				return true;
+			}
+			return false;
+		
+		case '{':
+			if (parse_object(&s, out)) {
+				*sp = s;
+				return true;
+			}
+			return false;
+		
+		default: {
+			double num;
+			if (parse_number(&s, out ? &num : NULL)) {
+				if (out)
+					*out = json_mknumber(num);
+				*sp = s;
+				return true;
+			}
+			return false;
+		}
+	}
+}
+
+static bool parse_array(const char **sp, JsonNode **out)
+{
+	const char *s = *sp;
+	JsonNode *ret = out ? json_mkarray() : NULL;
+	JsonNode *element;
+	
+	if (*s++ != '[')
+		goto failure;
+	skip_space(&s);
+	
+	if (*s == ']') {
+		s++;
+		goto success;
+	}
+	
+	for (;;) {
+		if (!parse_value(&s, out ? &element : NULL))
+			goto failure;
+		skip_space(&s);
+		
+		if (out)
+			json_append_element(ret, element);
+		
+		if (*s == ']') {
+			s++;
+			goto success;
+		}
+		
+		if (*s++ != ',')
+			goto failure;
+		skip_space(&s);
+	}
+	
+success:
+	*sp = s;
+	if (out)
+		*out = ret;
+	return true;
+
+failure:
+	json_delete(ret);
+	return false;
+}
+
+static bool parse_object(const char **sp, JsonNode **out)
+{
+	const char *s = *sp;
+	JsonNode *ret = out ? json_mkobject() : NULL;
+	char *key;
+	JsonNode *value;
+	
+	if (*s++ != '{')
+		goto failure;
+	skip_space(&s);
+	
+	if (*s == '}') {
+		s++;
+		goto success;
+	}
+	
+	for (;;) {
+		if (!parse_string(&s, out ? &key : NULL))
+			goto failure;
+		skip_space(&s);
+		
+		if (*s++ != ':')
+			goto failure_free_key;
+		skip_space(&s);
+		
+		if (!parse_value(&s, out ? &value : NULL))
+			goto failure_free_key;
+		skip_space(&s);
+		
+		if (out)
+			append_member(ret, key, value);
+		
+		if (*s == '}') {
+			s++;
+			goto success;
+		}
+		
+		if (*s++ != ',')
+			goto failure;
+		skip_space(&s);
+	}
+	
+success:
+	*sp = s;
+	if (out)
+		*out = ret;
+	return true;
+
+failure_free_key:
+	if (out)
+		free(key);
+failure:
+	json_delete(ret);
+	return false;
+}
+
+bool parse_string(const char **sp, char **out)
+{
+	const char *s = *sp;
+	SB sb = { NULL, NULL, NULL };
+	char throwaway_buffer[4];
+		/* enough space for a UTF-8 character */
+	char *b;
+	
+	if (*s++ != '"')
+		return false;
+	
+	if (out) {
+		sb_init(&sb);
+		sb_need(&sb, 4);
+		b = sb.cur;
+	} else {
+		b = throwaway_buffer;
+	}
+	
+	while (*s != '"') {
+		unsigned char c = *s++;
+		
+		/* Parse next character, and write it to b. */
+		if (c == '\\') {
+			c = *s++;
+			switch (c) {
+				case '"':
+				case '\\':
+				case '/':
+					*b++ = c;
+					break;
+				case 'b':
+					*b++ = '\b';
+					break;
+				case 'f':
+					*b++ = '\f';
+					break;
+				case 'n':
+					*b++ = '\n';
+					break;
+				case 'r':
+					*b++ = '\r';
+					break;
+				case 't':
+					*b++ = '\t';
+					break;
+				case 'u':
+				{
+					uint16_t uc, lc;
+					uchar_t unicode;
+					
+					if (!parse_hex16(&s, &uc))
+						goto failed;
+					
+					if (uc >= 0xD800 && uc <= 0xDFFF) {
+						/* Handle UTF-16 surrogate pair. */
+						if (*s++ != '\\' || *s++ != 'u' || !parse_hex16(&s, &lc))
+							goto failed; /* Incomplete surrogate pair. */
+						if (!from_surrogate_pair(uc, lc, &unicode))
+							goto failed; /* Invalid surrogate pair. */
+					} else if (uc == 0) {
+						/* Disallow "\u0000". */
+						goto failed;
+					} else {
+						unicode = uc;
+					}
+					
+					b += utf8_write_char(unicode, b);
+					break;
+				}
+				default:
+					/* Invalid escape */
+					goto failed;
+			}
+		} else if (c <= 0x1F) {
+			/* Control characters are not allowed in string literals. */
+			goto failed;
+		} else {
+			/* Validate and echo a UTF-8 character. */
+			int len;
+			
+			s--;
+			len = utf8_validate_cz(s);
+			if (len == 0)
+				goto failed; /* Invalid UTF-8 character. */
+			
+			while (len--)
+				*b++ = *s++;
+		}
+		
+		/*
+		 * Update sb to know about the new bytes,
+		 * and set up b to write another character.
+		 */
+		if (out) {
+			sb.cur = b;
+			sb_need(&sb, 4);
+			b = sb.cur;
+		} else {
+			b = throwaway_buffer;
+		}
+	}
+	s++;
+	
+	if (out)
+		*out = sb_finish(&sb);
+	*sp = s;
+	return true;
+
+failed:
+	if (out)
+		sb_free(&sb);
+	return false;
+}
+
+/*
+ * The JSON spec says that a number shall follow this precise pattern
+ * (spaces and quotes added for readability):
+ *	 '-'? (0 | [1-9][0-9]*) ('.' [0-9]+)? ([Ee] [+-]? [0-9]+)?
+ *
+ * However, some JSON parsers are more liberal.  For instance, PHP accepts
+ * '.5' and '1.'.  JSON.parse accepts '+3'.
+ *
+ * This function takes the strict approach.
+ */
+bool parse_number(const char **sp, double *out)
+{
+	const char *s = *sp;
+
+	/* '-'? */
+	if (*s == '-')
+		s++;
+
+	/* (0 | [1-9][0-9]*) */
+	if (*s == '0') {
+		s++;
+	} else {
+		if (!is_digit(*s))
+			return false;
+		do {
+			s++;
+		} while (is_digit(*s));
+	}
+
+	/* ('.' [0-9]+)? */
+	if (*s == '.') {
+		s++;
+		if (!is_digit(*s))
+			return false;
+		do {
+			s++;
+		} while (is_digit(*s));
+	}
+
+	/* ([Ee] [+-]? [0-9]+)? */
+	if (*s == 'E' || *s == 'e') {
+		s++;
+		if (*s == '+' || *s == '-')
+			s++;
+		if (!is_digit(*s))
+			return false;
+		do {
+			s++;
+		} while (is_digit(*s));
+	}
+
+	if (out)
+		*out = strtod(*sp, NULL);
+
+	*sp = s;
+	return true;
+}
+
+static void skip_space(const char **sp)
+{
+	const char *s = *sp;
+	while (is_space(*s))
+		s++;
+	*sp = s;
+}
+
+static void emit_value(SB *out, const JsonNode *node)
+{
+	assert(tag_is_valid(node->tag));
+	switch (node->tag) {
+		case JSON_NULL:
+			sb_puts(out, "null");
+			break;
+		case JSON_BOOL:
+			sb_puts(out, node->bool_ ? "true" : "false");
+			break;
+		case JSON_STRING:
+			emit_string(out, node->string_);
+			break;
+		case JSON_NUMBER:
+			emit_number(out, node->number_);
+			break;
+		case JSON_ARRAY:
+			emit_array(out, node);
+			break;
+		case JSON_OBJECT:
+			emit_object(out, node);
+			break;
+		default:
+			assert(false);
+	}
+}
+
+void emit_value_indented(SB *out, const JsonNode *node, const char *space, int indent_level)
+{
+	assert(tag_is_valid(node->tag));
+	switch (node->tag) {
+		case JSON_NULL:
+			sb_puts(out, "null");
+			break;
+		case JSON_BOOL:
+			sb_puts(out, node->bool_ ? "true" : "false");
+			break;
+		case JSON_STRING:
+			emit_string(out, node->string_);
+			break;
+		case JSON_NUMBER:
+			emit_number(out, node->number_);
+			break;
+		case JSON_ARRAY:
+			emit_array_indented(out, node, space, indent_level);
+			break;
+		case JSON_OBJECT:
+			emit_object_indented(out, node, space, indent_level);
+			break;
+		default:
+			assert(false);
+	}
+}
+
+static void emit_array(SB *out, const JsonNode *array)
+{
+	const JsonNode *element;
+	
+	sb_putc(out, '[');
+	json_foreach(element, array) {
+		emit_value(out, element);
+		if (element->next != NULL)
+			sb_putc(out, ',');
+	}
+	sb_putc(out, ']');
+}
+
+static void emit_array_indented(SB *out, const JsonNode *array, const char *space, int indent_level)
+{
+	const JsonNode *element = array->children.head;
+	int i;
+	
+	if (element == NULL) {
+		sb_puts(out, "[]");
+		return;
+	}
+	
+	sb_puts(out, "[\n");
+	while (element != NULL) {
+		for (i = 0; i < indent_level + 1; i++)
+			sb_puts(out, space);
+		emit_value_indented(out, element, space, indent_level + 1);
+		
+		element = element->next;
+		sb_puts(out, element != NULL ? ",\n" : "\n");
+	}
+	for (i = 0; i < indent_level; i++)
+		sb_puts(out, space);
+	sb_putc(out, ']');
+}
+
+static void emit_object(SB *out, const JsonNode *object)
+{
+	const JsonNode *member;
+	
+	sb_putc(out, '{');
+	json_foreach(member, object) {
+		emit_string(out, member->key);
+		sb_putc(out, ':');
+		emit_value(out, member);
+		if (member->next != NULL)
+			sb_putc(out, ',');
+	}
+	sb_putc(out, '}');
+}
+
+static void emit_object_indented(SB *out, const JsonNode *object, const char *space, int indent_level)
+{
+	const JsonNode *member = object->children.head;
+	int i;
+	
+	if (member == NULL) {
+		sb_puts(out, "{}");
+		return;
+	}
+	
+	sb_puts(out, "{\n");
+	while (member != NULL) {
+		for (i = 0; i < indent_level + 1; i++)
+			sb_puts(out, space);
+		emit_string(out, member->key);
+		sb_puts(out, ": ");
+		emit_value_indented(out, member, space, indent_level + 1);
+		
+		member = member->next;
+		sb_puts(out, member != NULL ? ",\n" : "\n");
+	}
+	for (i = 0; i < indent_level; i++)
+		sb_puts(out, space);
+	sb_putc(out, '}');
+}
+
+void emit_string(SB *out, const char *str)
+{
+	bool escape_unicode = false;
+	const char *s = str;
+	char *b;
+	
+	assert(utf8_validate(str));
+	
+	/*
+	 * 14 bytes is enough space to write up to two
+	 * \uXXXX escapes and two quotation marks.
+	 */
+	sb_need(out, 14);
+	b = out->cur;
+	
+	*b++ = '"';
+	while (*s != 0) {
+		unsigned char c = *s++;
+		
+		/* Encode the next character, and write it to b. */
+		switch (c) {
+			case '"':
+				*b++ = '\\';
+				*b++ = '"';
+				break;
+			case '\\':
+				*b++ = '\\';
+				*b++ = '\\';
+				break;
+			case '\b':
+				*b++ = '\\';
+				*b++ = 'b';
+				break;
+			case '\f':
+				*b++ = '\\';
+				*b++ = 'f';
+				break;
+			case '\n':
+				*b++ = '\\';
+				*b++ = 'n';
+				break;
+			case '\r':
+				*b++ = '\\';
+				*b++ = 'r';
+				break;
+			case '\t':
+				*b++ = '\\';
+				*b++ = 't';
+				break;
+			default: {
+				int len;
+				
+				s--;
+				len = utf8_validate_cz(s);
+				
+				if (len == 0) {
+					/*
+					 * Handle invalid UTF-8 character gracefully in production
+					 * by writing a replacement character (U+FFFD)
+					 * and skipping a single byte.
+					 *
+					 * This should never happen when assertions are enabled
+					 * due to the assertion at the beginning of this function.
+					 */
+					assert(false);
+					if (escape_unicode) {
+						strcpy(b, "\\uFFFD");
+						b += 6;
+					} else {
+						*b++ = (char)0xEF;
+						*b++ = (char)0xBF;
+						*b++ = (char)0xBD;
+					}
+					s++;
+				} else if (c < 0x1F || (c >= 0x80 && escape_unicode)) {
+					/* Encode using \u.... */
+					uint32_t unicode;
+					
+					s += utf8_read_char(s, &unicode);
+					
+					if (unicode <= 0xFFFF) {
+						*b++ = '\\';
+						*b++ = 'u';
+						b += write_hex16(b, unicode);
+					} else {
+						/* Produce a surrogate pair. */
+						uint16_t uc, lc;
+						assert(unicode <= 0x10FFFF);
+						to_surrogate_pair(unicode, &uc, &lc);
+						*b++ = '\\';
+						*b++ = 'u';
+						b += write_hex16(b, uc);
+						*b++ = '\\';
+						*b++ = 'u';
+						b += write_hex16(b, lc);
+					}
+				} else {
+					/* Write the character directly. */
+					while (len--)
+						*b++ = *s++;
+				}
+				
+				break;
+			}
+		}
+	
+		/*
+		 * Update *out to know about the new bytes,
+		 * and set up b to write another encoded character.
+		 */
+		out->cur = b;
+		sb_need(out, 14);
+		b = out->cur;
+	}
+	*b++ = '"';
+	
+	out->cur = b;
+}
+
+static void emit_number(SB *out, double num)
+{
+	/*
+	 * This isn't exactly how JavaScript renders numbers,
+	 * but it should produce valid JSON for reasonable numbers
+	 * preserve precision well enough, and avoid some oddities
+	 * like 0.3 -> 0.299999999999999988898 .
+	 */
+	char buf[64];
+	sprintf(buf, "%.16g", num);
+	
+	if (number_is_valid(buf))
+		sb_puts(out, buf);
+	else
+		sb_puts(out, "null");
+}
+
+static bool tag_is_valid(unsigned int tag)
+{
+	return (/* tag >= JSON_NULL && */ tag <= JSON_OBJECT);
+}
+
+static bool number_is_valid(const char *num)
+{
+	return (parse_number(&num, NULL) && *num == '\0');
+}
+
+static bool expect_literal(const char **sp, const char *str)
+{
+	const char *s = *sp;
+	
+	while (*str != '\0')
+		if (*s++ != *str++)
+			return false;
+	
+	*sp = s;
+	return true;
+}
+
+/*
+ * Parses exactly 4 hex characters (capital or lowercase).
+ * Fails if any input chars are not [0-9A-Fa-f].
+ */
+static bool parse_hex16(const char **sp, uint16_t *out)
+{
+	const char *s = *sp;
+	uint16_t ret = 0;
+	uint16_t i;
+	uint16_t tmp;
+	char c;
+
+	for (i = 0; i < 4; i++) {
+		c = *s++;
+		if (c >= '0' && c <= '9')
+			tmp = c - '0';
+		else if (c >= 'A' && c <= 'F')
+			tmp = c - 'A' + 10;
+		else if (c >= 'a' && c <= 'f')
+			tmp = c - 'a' + 10;
+		else
+			return false;
+
+		ret <<= 4;
+		ret += tmp;
+	}
+	
+	if (out)
+		*out = ret;
+	*sp = s;
+	return true;
+}
+
+/*
+ * Encodes a 16-bit number into hexadecimal,
+ * writing exactly 4 hex chars.
+ */
+static int write_hex16(char *out, uint16_t val)
+{
+	const char *hex = "0123456789ABCDEF";
+	
+	*out++ = hex[(val >> 12) & 0xF];
+	*out++ = hex[(val >> 8)  & 0xF];
+	*out++ = hex[(val >> 4)  & 0xF];
+	*out++ = hex[ val        & 0xF];
+	
+	return 4;
+}
+
+bool json_check(const JsonNode *node, char errmsg[256])
+{
+	#define problem(...) do { \
+			if (errmsg != NULL) \
+				snprintf(errmsg, 256, __VA_ARGS__); \
+			return false; \
+		} while (0)
+	
+	if (node->key != NULL && !utf8_validate(node->key))
+		problem("key contains invalid UTF-8");
+	
+	if (!tag_is_valid(node->tag))
+		problem("tag is invalid (%u)", node->tag);
+	
+	if (node->tag == JSON_BOOL) {
+		if (node->bool_ != false && node->bool_ != true)
+			problem("bool_ is neither false (%d) nor true (%d)", (int)false, (int)true);
+	} else if (node->tag == JSON_STRING) {
+		if (node->string_ == NULL)
+			problem("string_ is NULL");
+		if (!utf8_validate(node->string_))
+			problem("string_ contains invalid UTF-8");
+	} else if (node->tag == JSON_ARRAY || node->tag == JSON_OBJECT) {
+		JsonNode *head = node->children.head;
+		JsonNode *tail = node->children.tail;
+		
+		if (head == NULL || tail == NULL) {
+			if (head != NULL)
+				problem("tail is NULL, but head is not");
+			if (tail != NULL)
+				problem("head is NULL, but tail is not");
+		} else {
+			JsonNode *child;
+			JsonNode *last = NULL;
+			
+			if (head->prev != NULL)
+				problem("First child's prev pointer is not NULL");
+			
+			for (child = head; child != NULL; last = child, child = child->next) {
+				if (child == node)
+					problem("node is its own child");
+				if (child->next == child)
+					problem("child->next == child (cycle)");
+				if (child->next == head)
+					problem("child->next == head (cycle)");
+				
+				if (child->parent != node)
+					problem("child does not point back to parent");
+				if (child->next != NULL && child->next->prev != child)
+					problem("child->next does not point back to child");
+				
+				if (node->tag == JSON_ARRAY && child->key != NULL)
+					problem("Array element's key is not NULL");
+				if (node->tag == JSON_OBJECT && child->key == NULL)
+					problem("Object member's key is NULL");
+				
+				if (!json_check(child, errmsg))
+					return false;
+			}
+			
+			if (last != tail)
+				problem("tail does not match pointer found by starting at head and following next links");
+		}
+	}
+	
+	return true;
+	
+	#undef problem
+}