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Date: Mon, 4 Jan 2016 14:25:00 +0100
From: Jan Kara <jack@...e.cz>
To: Andrew Gabbasov <andrew_gabbasov@...tor.com>
Cc: Jan Kara <jack@...e.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 7/7] udf: Merge linux specific translation into CS0
conversion function
On Thu 24-12-15 10:25:38, Andrew Gabbasov wrote:
> Current implementation of udf_translate_to_linux function does not
> support multi-bytes characters at all: it counts bytes while calculating
> extension length, when inserting CRC inside the name it doesn't
> take into account inter-character boundaries and can break into
> the middle of the character.
>
> The most efficient way to properly support multi-bytes characters is
> merging of translation operations directly into conversion function.
> This can help to avoid extra passes along the string or parsing
> the multi-bytes character back into unicode to find out it's length.
>
> Signed-off-by: Andrew Gabbasov <andrew_gabbasov@...tor.com>
Looks mostly good. A few comments below.
> ---
> fs/udf/unicode.c | 260 ++++++++++++++++++++++++++++++-------------------------
> 1 file changed, 141 insertions(+), 119 deletions(-)
>
> diff --git a/fs/udf/unicode.c b/fs/udf/unicode.c
> index f1cdeac..1dc967d 100644
> --- a/fs/udf/unicode.c
> +++ b/fs/udf/unicode.c
> @@ -28,9 +28,6 @@
>
> #include "udf_sb.h"
>
> -static int udf_translate_to_linux(uint8_t *, int, const uint8_t *, int,
> - const uint8_t *, int);
> -
> static int udf_uni2char_utf8(wchar_t uni,
> unsigned char *out,
> int boundlen)
> @@ -114,13 +111,32 @@ static int udf_char2uni_utf8(const unsigned char *in,
> return u_len;
> }
>
> +#define ILLEGAL_CHAR_MARK '_'
> +#define EXT_MARK '.'
> +#define CRC_MARK '#'
> +#define EXT_SIZE 5
> +/* Number of chars we need to store generated CRC to make filename unique */
> +#define CRC_LEN 5
> +
> static int udf_name_from_CS0(uint8_t *str_o, int str_max_len,
> const uint8_t *ocu, int ocu_len,
> - int (*conv_f)(wchar_t, unsigned char *, int))
> + int (*conv_f)(wchar_t, unsigned char *, int),
> + int translate)
> {
> + uint32_t c;
> uint8_t cmp_id;
> int i, len;
> - int str_o_len = 0;
> + int u_ch;
> + int firstDots = 0, needsCRC = 0, illChar;
> + int ext_i_len, ext_max_len;
> + int str_o_len = 0; /* Length of resulting output */
> + int ext_o_len = 0; /* Extension output length */
> + int ext_crc_len = 0; /* Extension output length if used with CRC */
> + int i_ext = -1; /* Extension position in input buffer */
> + int o_crc = 0; /* Rightmost possible output pos for CRC+ext */
> + unsigned short valueCRC;
> + uint8_t ext[EXT_SIZE * NLS_MAX_CHARSET_SIZE + 1];
> + uint8_t crc[CRC_LEN];
>
> if (str_max_len <= 0)
> return 0;
> @@ -133,22 +149,134 @@ static int udf_name_from_CS0(uint8_t *str_o, int str_max_len,
> cmp_id = ocu[0];
> if (cmp_id != 8 && cmp_id != 16) {
> memset(str_o, 0, str_max_len);
> - pr_err("unknown compression code (%d) stri=%s\n", cmp_id, ocu);
> + pr_err("unknown compression code (%d)\n", cmp_id);
> return -EINVAL;
> }
> + u_ch = cmp_id >> 3;
> +
> + ocu++;
> + ocu_len--;
> +
Can we just check whether ocu_len is a multiple of u_ch here and bail out
if not? That would save us some rounding below and also fix possible access
beyond the end of the string in case fs is corrupted.
> + if (translate) {
> + /* Look for extension */
> + for (i = (ocu_len & ~(u_ch - 1)) - u_ch, ext_i_len = 0;
> + (i >= 0) && (ext_i_len < EXT_SIZE);
> + i -= u_ch, ext_i_len++) {
> +
Just remove the empty line above please.
> + c = ocu[i];
> + if (u_ch > 1)
> + c = (c << 8) | ocu[i + 1];
> +
> + if (c == EXT_MARK) {
> + if (ext_i_len)
> + i_ext = i;
> + break;
> + }
> + }
> + if (i_ext >= 0) {
> + /* Convert extension */
> + ext_max_len = min_t(int, sizeof(ext), str_max_len);
> + ext[ext_o_len++] = EXT_MARK;
> + illChar = 0;
> + for (i = i_ext + u_ch; i < ocu_len;) {
> +
Remove the empty line here please. Also how about using i += u_ch in the
for() above instead of i++ in the two lines below?
> + c = ocu[i++];
> + if (u_ch > 1)
> + c = (c << 8) | ocu[i++];
> +
> + if (c == '/' || c == 0) {
> + if (illChar)
> + continue;
> + illChar = 1;
> + needsCRC = 1;
> + c = ILLEGAL_CHAR_MARK;
> + } else {
> + illChar = 0;
> + }
> +
> + len = conv_f(c, &ext[ext_o_len],
> + ext_max_len - ext_o_len);
> + /* Valid character? */
> + if (len >= 0) {
> + ext_o_len += len;
> + } else {
> + ext[ext_o_len++] = '?';
> + needsCRC = 1;
> + }
> + if ((ext_o_len + CRC_LEN) < str_max_len)
> + ext_crc_len = ext_o_len;
> + }
> + }
> + }
> +
> + illChar = 0;
> + for (i = 0; i < ocu_len;) {
> +
Again, remove the empty line, i += u_ch.
> + if (str_o_len >= str_max_len) {
> + needsCRC = 1;
> + break;
> + }
> +
> + if (translate && (i == i_ext)) {
> + if (str_o_len > (str_max_len - ext_o_len))
> + needsCRC = 1;
> + break;
> + }
>
> - for (i = 1; (i < ocu_len) && (str_o_len < str_max_len);) {
> /* Expand OSTA compressed Unicode to Unicode */
> - uint32_t c = ocu[i++];
> - if (cmp_id == 16)
> + c = ocu[i++];
> + if (u_ch > 1)
> c = (c << 8) | ocu[i++];
>
> + if (translate) {
> + if ((c == '.') && (firstDots >= 0))
> + firstDots++;
> + else
> + firstDots = -1;
> +
> + if (c == '/' || c == 0) {
> + if (illChar)
> + continue;
> + illChar = 1;
> + needsCRC = 1;
> + c = ILLEGAL_CHAR_MARK;
> + } else {
> + illChar = 0;
> + }
> + }
> +
> len = conv_f(c, &str_o[str_o_len], str_max_len - str_o_len);
> /* Valid character? */
> - if (len >= 0)
> + if (len >= 0) {
> str_o_len += len;
> - else
> + } else {
> str_o[str_o_len++] = '?';
> + needsCRC = 1;
> + }
Umm, can you try factoring out body of this loop into a helper function and
using it both during extension parsing and full name parsing? Also I think
that checking whether the name is '.' or '..' could be moved just into the
if (translate) below where you could just directly check it like:
if (str_o_len <= 2 && str_o[0] == '.' &&
(str_o_len == 1 || str_o[1] == '.'))
> + if (str_o_len <= (str_max_len - ext_o_len - CRC_LEN))
> + o_crc = str_o_len;
> + }
> +
> + if (translate) {
> + if ((firstDots == 1) || (firstDots == 2))
> + needsCRC = 1;
> + if (needsCRC) {
> + str_o_len = o_crc;
> + valueCRC = crc_itu_t(0, ocu, ocu_len);
> + crc[0] = CRC_MARK;
> + crc[1] = hex_asc_upper_hi(valueCRC >> 8);
> + crc[2] = hex_asc_upper_lo(valueCRC >> 8);
> + crc[3] = hex_asc_upper_hi(valueCRC);
> + crc[4] = hex_asc_upper_lo(valueCRC);
> + len = min_t(int, CRC_LEN, str_max_len - str_o_len);
> + memcpy(&str_o[str_o_len], crc, len);
> + str_o_len += len;
> + ext_o_len = ext_crc_len;
> + }
> + if (ext_o_len > 0) {
> + memcpy(&str_o[str_o_len], ext, ext_o_len);
> + str_o_len += ext_o_len;
> + }
> }
>
> return str_o_len;
Honza
--
Jan Kara <jack@...e.com>
SUSE Labs, CR
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