[PATCH] NLS support for ASCII

I created an ASCII NSL module manually based on the ISO-8859-1 NLS module.

This might be of use for people who do not want any charset conversion to
take place.  fs modules like vfat for example then could be forced to
display any non-ASCII character in the uni_xlate escaped form.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/nls/Kconfig

@@ -332,6 +332,14 @@ config NLS_CODEPAGE_1251
 	  say Y here if you want to include the DOS codepage for Russian and
 	  Bulgarian and Belarusian.
 
+config NLS_ASCII
+	tristate "ASCII (United States)"
+	depends on NLS
+	help
+	  An ASCII NLS module is needed if you want to override the
+	  DEFAULT NLS with this very basic charset and don't want any
+	  non-ASCII characters to be translated.
+
 config NLS_ISO8859_1
 	tristate "NLS ISO 8859-1  (Latin 1; Western European Languages)"
 	depends on NLS

fs/nls/Makefile

@@ -26,6 +26,7 @@ obj-$(CONFIG_NLS_CODEPAGE_949)	+= nls_cp949.o
 obj-$(CONFIG_NLS_CODEPAGE_950)	+= nls_cp950.o
 obj-$(CONFIG_NLS_CODEPAGE_1250) += nls_cp1250.o
 obj-$(CONFIG_NLS_CODEPAGE_1251)	+= nls_cp1251.o
+obj-$(CONFIG_NLS_ASCII)		+= nls_ascii.o
 obj-$(CONFIG_NLS_ISO8859_1)	+= nls_iso8859-1.o
 obj-$(CONFIG_NLS_ISO8859_2)	+= nls_iso8859-2.o
 obj-$(CONFIG_NLS_ISO8859_3)	+= nls_iso8859-3.o

fs/nls/nls_ascii.c

+/*
+ * linux/fs/nls_ascii.c
+ *
+ * Charset ascii translation tables.
+ * Generated automatically from the Unicode and charset
+ * tables from the Unicode Organization (www.unicode.org).
+ * The Unicode to charset table has only exact mappings.
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/string.h>
+#include <linux/nls.h>
+#include <linux/errno.h>
+
+static wchar_t charset2uni[128] = {
+	/* 0x00*/
+	0x0000, 0x0001, 0x0002, 0x0003,
+	0x0004, 0x0005, 0x0006, 0x0007,
+	0x0008, 0x0009, 0x000a, 0x000b,
+	0x000c, 0x000d, 0x000e, 0x000f,
+	/* 0x10*/
+	0x0010, 0x0011, 0x0012, 0x0013,
+	0x0014, 0x0015, 0x0016, 0x0017,
+	0x0018, 0x0019, 0x001a, 0x001b,
+	0x001c, 0x001d, 0x001e, 0x001f,
+	/* 0x20*/
+	0x0020, 0x0021, 0x0022, 0x0023,
+	0x0024, 0x0025, 0x0026, 0x0027,
+	0x0028, 0x0029, 0x002a, 0x002b,
+	0x002c, 0x002d, 0x002e, 0x002f,
+	/* 0x30*/
+	0x0030, 0x0031, 0x0032, 0x0033,
+	0x0034, 0x0035, 0x0036, 0x0037,
+	0x0038, 0x0039, 0x003a, 0x003b,
+	0x003c, 0x003d, 0x003e, 0x003f,
+	/* 0x40*/
+	0x0040, 0x0041, 0x0042, 0x0043,
+	0x0044, 0x0045, 0x0046, 0x0047,
+	0x0048, 0x0049, 0x004a, 0x004b,
+	0x004c, 0x004d, 0x004e, 0x004f,
+	/* 0x50*/
+	0x0050, 0x0051, 0x0052, 0x0053,
+	0x0054, 0x0055, 0x0056, 0x0057,
+	0x0058, 0x0059, 0x005a, 0x005b,
+	0x005c, 0x005d, 0x005e, 0x005f,
+	/* 0x60*/
+	0x0060, 0x0061, 0x0062, 0x0063,
+	0x0064, 0x0065, 0x0066, 0x0067,
+	0x0068, 0x0069, 0x006a, 0x006b,
+	0x006c, 0x006d, 0x006e, 0x006f,
+	/* 0x70*/
+	0x0070, 0x0071, 0x0072, 0x0073,
+	0x0074, 0x0075, 0x0076, 0x0077,
+	0x0078, 0x0079, 0x007a, 0x007b,
+	0x007c, 0x007d, 0x007e, 0x007f,
+};
+
+static unsigned char page00[128] = {
+	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, /* 0x00-0x07 */
+	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, /* 0x08-0x0f */
+	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, /* 0x10-0x17 */
+	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, /* 0x18-0x1f */
+	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, /* 0x20-0x27 */
+	0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, /* 0x28-0x2f */
+	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, /* 0x30-0x37 */
+	0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, /* 0x38-0x3f */
+	0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, /* 0x40-0x47 */
+	0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, /* 0x48-0x4f */
+	0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, /* 0x50-0x57 */
+	0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, /* 0x58-0x5f */
+	0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, /* 0x60-0x67 */
+	0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, /* 0x68-0x6f */
+	0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, /* 0x70-0x77 */
+	0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, /* 0x78-0x7f */
+};
+
+static unsigned char *page_uni2charset[128] = {
+	page00, NULL,   NULL,   NULL,   NULL,   NULL,   NULL,   NULL,
+};
+
+static unsigned char charset2lower[128] = {
+	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, /* 0x00-0x07 */
+	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, /* 0x08-0x0f */
+	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, /* 0x10-0x17 */
+	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, /* 0x18-0x1f */
+	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, /* 0x20-0x27 */
+	0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, /* 0x28-0x2f */
+	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, /* 0x30-0x37 */
+	0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, /* 0x38-0x3f */
+	0x40, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, /* 0x40-0x47 */
+	0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, /* 0x48-0x4f */
+	0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, /* 0x50-0x57 */
+	0x78, 0x79, 0x7a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, /* 0x58-0x5f */
+	0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67, /* 0x60-0x67 */
+	0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f, /* 0x68-0x6f */
+	0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77, /* 0x70-0x77 */
+	0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, /* 0x78-0x7f */
+};
+
+static unsigned char charset2upper[128] = {
+	0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, /* 0x00-0x07 */
+	0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f, /* 0x08-0x0f */
+	0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, /* 0x10-0x17 */
+	0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f, /* 0x18-0x1f */
+	0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, /* 0x20-0x27 */
+	0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f, /* 0x28-0x2f */
+	0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, /* 0x30-0x37 */
+	0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, /* 0x38-0x3f */
+	0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, /* 0x40-0x47 */
+	0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, /* 0x48-0x4f */
+	0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, /* 0x50-0x57 */
+	0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f, /* 0x58-0x5f */
+	0x60, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, /* 0x60-0x67 */
+	0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, /* 0x68-0x6f */
+	0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, /* 0x70-0x77 */
+	0x58, 0x59, 0x5a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f, /* 0x78-0x7f */
+};
+
+static int uni2char(wchar_t uni, unsigned char *out, int boundlen)
+{
+	unsigned char *uni2charset;
+	unsigned char cl = uni & 0x00ff;
+	unsigned char ch = (uni & 0xff00) >> 8;
+
+	if (boundlen <= 0)
+		return -ENAMETOOLONG;
+
+	uni2charset = page_uni2charset[ch];
+	if (uni2charset && uni2charset[cl])
+		out[0] = uni2charset[cl];
+	else
+		return -EINVAL;
+	return 1;
+}
+
+static int char2uni(const unsigned char *rawstring, int boundlen, wchar_t *uni)
+{
+	*uni = charset2uni[*rawstring];
+	if (*uni == 0x0000)
+		return -EINVAL;
+	return 1;
+}
+
+static struct nls_table table = {
+	.charset	= "ascii",
+	.uni2char	= uni2char,
+	.char2uni	= char2uni,
+	.charset2lower	= charset2lower,
+	.charset2upper	= charset2upper,
+	.owner		= THIS_MODULE,
+};
+
+static int __init init_nls_ascii(void)
+{
+	return register_nls(&table);
+}
+
+static void __exit exit_nls_ascii(void)
+{
+	unregister_nls(&table);
+}
+
+module_init(init_nls_ascii)
+module_exit(exit_nls_ascii)
+
+MODULE_LICENSE("Dual BSD/GPL");