Import beginnings of a CSS parsing library.

Currently comprises a lexer.

svn path=/trunk/libcss/; revision=4112

1 files changed, 161 insertions, 0 deletions

diff --git a/src/charset/detect.c b/src/charset/detect.c
new file mode 100644
index 0000000..11ee699
--- /dev/null
+++ b/src/charset/detect.c
@@ -0,0 +1,161 @@
+/*
+ * This file is part of LibCSS.
+ * Licensed under the MIT License,
+ *                http://www.opensource.org/licenses/mit-license.php
+ * Copyright 2008 John-Mark Bell <jmb@netsurf-browser.org>
+ */
+
+#include <stdbool.h>
+#include <string.h>
+
+#include <parserutils/charset/mibenum.h>
+
+#include "charset/detect.h"
+#include "utils/utils.h"
+
+static parserutils_error css_charset_read_bom_or_charset(const uint8_t *data, 
+		size_t len, uint16_t *mibenum);
+
+/**
+ * Extract a charset from a chunk of data
+ *
+ * \param data     Pointer to buffer containing data
+ * \param len      Buffer length
+ * \param mibenum  Pointer to location containing current MIB enum
+ * \param source   Pointer to location containing current charset source
+ * \return PARSERUTILS_OK on success, appropriate error otherwise
+ *
+ * ::mibenum and ::source will be updated on exit
+ *
+ * CSS 2.1 $4.4
+ */
+parserutils_error css_charset_extract(const uint8_t *data, size_t len,
+		uint16_t *mibenum, uint32_t *source)
+{
+	css_error error;
+	uint16_t charset = 0;
+
+	if (data == NULL || mibenum == NULL || source == NULL)
+		return PARSERUTILS_BADPARM;
+
+	/* If the charset was dictated by the client, we've nothing to detect */
+	if (*source == CSS_CHARSET_DICTATED)
+		return PARSERUTILS_OK;
+
+	/* We need at least 4 bytes of data */
+	if (len < 4)
+		goto default_encoding;
+
+	/* Look for a BOM and/or @charset */
+	error = css_charset_read_bom_or_charset(data, len, &charset);
+	if (error != PARSERUTILS_OK)
+		return error;
+
+	if (charset != 0) {
+		*mibenum = charset;
+		*source = CSS_CHARSET_DOCUMENT;
+
+		return PARSERUTILS_OK;
+	}
+
+	/* If we've already got a charset from the linking mechanism or 
+	 * referring document, then we've nothing further to do */
+	if (*source != CSS_CHARSET_DEFAULT)
+		return PARSERUTILS_OK;
+
+	/* We've not yet found a charset, so use the default fallback */
+default_encoding:
+
+	charset = parserutils_charset_mibenum_from_name("UTF-8", SLEN("UTF-8"));
+
+	*mibenum = charset;
+	*source = CSS_CHARSET_DEFAULT;
+
+	return PARSERUTILS_OK;
+}
+
+
+/**
+ * Inspect the beginning of a buffer of data for the presence of a
+ * UTF Byte Order Mark and/or an @charset rule
+ *
+ * \param data     Pointer to buffer containing data
+ * \param len      Buffer length
+ * \param mibenum  Pointer to location to receive MIB enum
+ * \return PARSERUTILS_OK on success, appropriate error otherwise
+ */
+parserutils_error css_charset_read_bom_or_charset(const uint8_t *data, 
+		size_t len, uint16_t *mibenum)
+{
+	uint16_t charset = 0;
+
+	if (data == NULL)
+		return PARSERUTILS_BADPARM;
+
+	/* We require at least 4 bytes of data */
+	if (len < 4)
+		return PARSERUTILS_NEEDDATA;
+
+
+	/* Look for BOM */
+	if (data[0] == 0x00 && data[1] == 0x00 && 
+			data[2] == 0xFE && data[3] == 0xFF) {
+		charset = parserutils_charset_mibenum_from_name("UTF-32BE", 
+				SLEN("UTF-32BE"));
+	} else if (data[0] == 0xFF && data[1] == 0xFE &&
+			data[2] == 0x00 && data[3] == 0x00) {
+		charset = parserutils_charset_mibenum_from_name("UTF-32LE", 
+				SLEN("UTF-32LE"));
+	} else if (data[0] == 0xFE && data[1] == 0xFF) {
+		charset = parserutils_charset_mibenum_from_name("UTF-16BE", 
+				SLEN("UTF-16BE"));
+	} else if (data[0] == 0xFF && data[1] == 0xFE) {
+		charset = parserutils_charset_mibenum_from_name("UTF-16LE", 
+				SLEN("UTF-16LE"));
+	} else if (data[0] == 0xEF && data[1] == 0xBB && data[2] == 0xBF) {
+		charset = parserutils_charset_mibenum_from_name("UTF-8", 
+				SLEN("UTF-8"));
+	}
+
+	/* BOM beats @charset.
+	 * UAs differ here, but none appear to match the spec. 
+	 * The spec indicates that any @charset present in conjunction with a 
+	 * BOM, should match the BOM. In reality, it appears UAs just take the 
+	 * BOM as gospel and ignore any @charset rule. The w3c CSS validator 
+	 * appears to do the same (at the least, it doesn't complain about a
+	 * mismatch).
+	 */
+	if (charset != 0) {
+		*mibenum = charset;
+		return PARSERUTILS_OK;
+	}
+
+	/** \todo UTF-32 and UTF-16 @charset support */
+
+	/* Look for @charset, assuming ASCII-compatible source data */
+	if (len > 10 &&	strncmp((const char *) data, "@charset \"", 
+			SLEN("@charset \"")) == 0) {
+		const uint8_t *end;
+
+		/* Look for "; at end of charset declaration */
+		for (end = data + 10; end < data + len; end++) {
+			if (*end == '"' && end < data + len - 1 && 
+					*(end + 1) == ';')
+				break;
+		}
+
+		if (end == data + len) {
+			/* Ran out of input */
+			return PARSERUTILS_NEEDDATA;
+		}
+
+		/* Convert to MIB enum */
+		charset = parserutils_charset_mibenum_from_name(
+				(char *) data + 10,  end - data - 10);
+	}
+
+	*mibenum = charset;
+
+	return PARSERUTILS_OK;
+}
+