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SubjectRe: [ 139/184] NLS: improve UTF8 -> UTF16 string conversion routine
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On Tue, 2013-06-04 at 19:23 +0200, Willy Tarreau wrote:
> 2.6.32-longterm review patch. If anyone has any objections, please let me know.
>
> ------------------
>
> From: Alan Stern <stern@rowland.harvard.edu>
>
> commit 0720a06a7518c9d0c0125bd5d1f3b6264c55c3dd upstream.
>
> The utf8s_to_utf16s conversion routine needs to be improved. Unlike
> its utf16s_to_utf8s sibling, it doesn't accept arguments specifying
> the maximum length of the output buffer or the endianness of its
> 16-bit output.
>
> This patch (as1501) adds the two missing arguments, and adjusts the
> only two places in the kernel where the function is called. A
> follow-on patch will add a third caller that does utilize the new
> capabilities.
>
> The two conversion routines are still annoyingly inconsistent in the
> way they handle invalid byte combinations. But that's a subject for a
> different patch.
>
> Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
> CC: Clemens Ladisch <clemens@ladisch.de>
> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
> [bwh: Bakckported to 2.6.32: drop Hyper-V change]

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

> Signed-off-by: Willy Tarreau <w@1wt.eu>
> ---
> fs/fat/namei_vfat.c | 3 ++-
> fs/nls/nls_base.c | 43 +++++++++++++++++++++++++++++++++----------
> include/linux/nls.h | 5 +++--
> 3 files changed, 38 insertions(+), 13 deletions(-)
>
> diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
> index 67b3df1..4251f35 100644
> --- a/fs/fat/namei_vfat.c
> +++ b/fs/fat/namei_vfat.c
> @@ -499,7 +499,8 @@ xlate_to_uni(const unsigned char *name, int len, unsigned char *outname,
> int charlen;
>
> if (utf8) {
> - *outlen = utf8s_to_utf16s(name, len, (wchar_t *)outname);
> + *outlen = utf8s_to_utf16s(name, len, UTF16_HOST_ENDIAN,
> + (wchar_t *) outname, FAT_LFN_LEN + 2);
> if (*outlen < 0)
> return *outlen;
> else if (*outlen > FAT_LFN_LEN)
> diff --git a/fs/nls/nls_base.c b/fs/nls/nls_base.c
> index 44a88a9..0eb059e 100644
> --- a/fs/nls/nls_base.c
> +++ b/fs/nls/nls_base.c
> @@ -114,34 +114,57 @@ int utf32_to_utf8(unicode_t u, u8 *s, int maxlen)
> }
> EXPORT_SYMBOL(utf32_to_utf8);
>
> -int utf8s_to_utf16s(const u8 *s, int len, wchar_t *pwcs)
> +static inline void put_utf16(wchar_t *s, unsigned c, enum utf16_endian endian)
> +{
> + switch (endian) {
> + default:
> + *s = (wchar_t) c;
> + break;
> + case UTF16_LITTLE_ENDIAN:
> + *s = __cpu_to_le16(c);
> + break;
> + case UTF16_BIG_ENDIAN:
> + *s = __cpu_to_be16(c);
> + break;
> + }
> +}
> +
> +int utf8s_to_utf16s(const u8 *s, int len, enum utf16_endian endian,
> + wchar_t *pwcs, int maxlen)
> {
> u16 *op;
> int size;
> unicode_t u;
>
> op = pwcs;
> - while (*s && len > 0) {
> + while (len > 0 && maxlen > 0 && *s) {
> if (*s & 0x80) {
> size = utf8_to_utf32(s, len, &u);
> if (size < 0)
> return -EINVAL;
> + s += size;
> + len -= size;
>
> if (u >= PLANE_SIZE) {
> + if (maxlen < 2)
> + break;
> u -= PLANE_SIZE;
> - *op++ = (wchar_t) (SURROGATE_PAIR |
> - ((u >> 10) & SURROGATE_BITS));
> - *op++ = (wchar_t) (SURROGATE_PAIR |
> + put_utf16(op++, SURROGATE_PAIR |
> + ((u >> 10) & SURROGATE_BITS),
> + endian);
> + put_utf16(op++, SURROGATE_PAIR |
> SURROGATE_LOW |
> - (u & SURROGATE_BITS));
> + (u & SURROGATE_BITS),
> + endian);
> + maxlen -= 2;
> } else {
> - *op++ = (wchar_t) u;
> + put_utf16(op++, u, endian);
> + maxlen--;
> }
> - s += size;
> - len -= size;
> } else {
> - *op++ = *s++;
> + put_utf16(op++, *s++, endian);
> len--;
> + maxlen--;
> }
> }
> return op - pwcs;
> diff --git a/include/linux/nls.h b/include/linux/nls.h
> index d47beef..5dc635f 100644
> --- a/include/linux/nls.h
> +++ b/include/linux/nls.h
> @@ -43,7 +43,7 @@ enum utf16_endian {
> UTF16_BIG_ENDIAN
> };
>
> -/* nls.c */
> +/* nls_base.c */
> extern int register_nls(struct nls_table *);
> extern int unregister_nls(struct nls_table *);
> extern struct nls_table *load_nls(char *);
> @@ -52,7 +52,8 @@ extern struct nls_table *load_nls_default(void);
>
> extern int utf8_to_utf32(const u8 *s, int len, unicode_t *pu);
> extern int utf32_to_utf8(unicode_t u, u8 *s, int maxlen);
> -extern int utf8s_to_utf16s(const u8 *s, int len, wchar_t *pwcs);
> +extern int utf8s_to_utf16s(const u8 *s, int len,
> + enum utf16_endian endian, wchar_t *pwcs, int maxlen);
> extern int utf16s_to_utf8s(const wchar_t *pwcs, int len,
> enum utf16_endian endian, u8 *s, int maxlen);
>

--
Ben Hutchings
Theory and practice are closer in theory than in practice.
- John Levine, moderator of comp.compilers
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