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    Subject[PATCH v2 2/3] lib/string_helpers.c: Refactor string_escape_mem
    Date
    When printf is given the format specifier %pE, it needs a way of
    obtaining the total output size that would be generated if the buffer
    was large enough, and string_escape_mem doesn't easily provide
    that. This is a refactorization of string_escape_mem in preparation of
    changing its external API to provide that information.

    Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
    ---
    lib/string_helpers.c | 182 ++++++++++++++++++++-------------------------------
    1 file changed, 72 insertions(+), 110 deletions(-)

    diff --git a/lib/string_helpers.c b/lib/string_helpers.c
    index 58b78ba57439..e14dd8555760 100644
    --- a/lib/string_helpers.c
    +++ b/lib/string_helpers.c
    @@ -243,29 +243,21 @@ int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
    }
    EXPORT_SYMBOL(string_unescape);

    -static int escape_passthrough(unsigned char c, char **dst, size_t *osz)
    +static bool escape_passthrough(unsigned char c, char **dst, char *end)
    {
    char *out = *dst;

    - if (*osz < 1)
    - return -ENOMEM;
    -
    - *out++ = c;
    -
    - *dst = out;
    - *osz -= 1;
    -
    - return 1;
    + if (out < end)
    + *out = c;
    + *dst = out + 1;
    + return true;
    }

    -static int escape_space(unsigned char c, char **dst, size_t *osz)
    +static bool escape_space(unsigned char c, char **dst, char *end)
    {
    char *out = *dst;
    unsigned char to;

    - if (*osz < 2)
    - return -ENOMEM;
    -
    switch (c) {
    case '\n':
    to = 'n';
    @@ -283,26 +275,23 @@ static int escape_space(unsigned char c, char **dst, size_t *osz)
    to = 'f';
    break;
    default:
    - return 0;
    + return false;
    }

    - *out++ = '\\';
    - *out++ = to;
    + if (out + 0 < end)
    + out[0] = '\\';
    + if (out + 1 < end)
    + out[1] = to;

    - *dst = out;
    - *osz -= 2;
    -
    - return 1;
    + *dst = out + 2;
    + return true;
    }

    -static int escape_special(unsigned char c, char **dst, size_t *osz)
    +static bool escape_special(unsigned char c, char **dst, char *end)
    {
    char *out = *dst;
    unsigned char to;

    - if (*osz < 2)
    - return -ENOMEM;
    -
    switch (c) {
    case '\\':
    to = '\\';
    @@ -314,71 +303,66 @@ static int escape_special(unsigned char c, char **dst, size_t *osz)
    to = 'e';
    break;
    default:
    - return 0;
    + return false;
    }

    - *out++ = '\\';
    - *out++ = to;
    + if (out + 0 < end)
    + out[0] = '\\';
    + if (out + 1 < end)
    + out[1] = to;

    - *dst = out;
    - *osz -= 2;
    -
    - return 1;
    + *dst = out + 2;
    + return true;
    }

    -static int escape_null(unsigned char c, char **dst, size_t *osz)
    +static bool escape_null(unsigned char c, char **dst, char *end)
    {
    char *out = *dst;

    - if (*osz < 2)
    - return -ENOMEM;
    -
    if (c)
    - return 0;
    -
    - *out++ = '\\';
    - *out++ = '0';
    + return false;

    - *dst = out;
    - *osz -= 2;
    + if (out + 0 < end)
    + out[0] = '\\';
    + if (out + 1 < end)
    + out[1] = '0';

    - return 1;
    + *dst = out + 2;
    + return true;
    }

    -static int escape_octal(unsigned char c, char **dst, size_t *osz)
    +static bool escape_octal(unsigned char c, char **dst, char *end)
    {
    char *out = *dst;

    - if (*osz < 4)
    - return -ENOMEM;
    -
    - *out++ = '\\';
    - *out++ = ((c >> 6) & 0x07) + '0';
    - *out++ = ((c >> 3) & 0x07) + '0';
    - *out++ = ((c >> 0) & 0x07) + '0';
    + if (out + 0 < end)
    + out[0] = '\\';
    + if (out + 1 < end)
    + out[1] = ((c >> 6) & 0x07) + '0';
    + if (out + 2 < end)
    + out[2] = ((c >> 3) & 0x07) + '0';
    + if (out + 3 < end)
    + out[3] = ((c >> 0) & 0x07) + '0';

    - *dst = out;
    - *osz -= 4;
    -
    - return 1;
    + *dst = out + 4;
    + return true;
    }

    -static int escape_hex(unsigned char c, char **dst, size_t *osz)
    +static bool escape_hex(unsigned char c, char **dst, char *end)
    {
    char *out = *dst;

    - if (*osz < 4)
    - return -ENOMEM;
    -
    - *out++ = '\\';
    - *out++ = 'x';
    - *out++ = hex_asc_hi(c);
    - *out++ = hex_asc_lo(c);
    -
    - *dst = out;
    - *osz -= 4;
    + if (out + 0 < end)
    + out[0] = '\\';
    + if (out + 1 < end)
    + out[1] = 'x';
    + if (out + 2 < end)
    + out[2] = hex_asc_hi(c);
    + if (out + 3 < end)
    + out[3] = hex_asc_lo(c);

    - return 1;
    + *dst = out + 4;
    + return true;
    }

    /**
    @@ -440,9 +424,10 @@ static int escape_hex(unsigned char c, char **dst, size_t *osz)
    int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
    unsigned int flags, const char *esc)
    {
    - char *out = *dst, *p = out;
    + char *p = *dst;
    + char *end = p + osz;
    bool is_dict = esc && *esc;
    - int ret = 0;
    + int ret;

    while (isz--) {
    unsigned char c = *src++;
    @@ -462,55 +447,32 @@ int string_escape_mem(const char *src, size_t isz, char **dst, size_t osz,
    (is_dict && !strchr(esc, c))) {
    /* do nothing */
    } else {
    - if (flags & ESCAPE_SPACE) {
    - ret = escape_space(c, &p, &osz);
    - if (ret < 0)
    - break;
    - if (ret > 0)
    - continue;
    - }
    -
    - if (flags & ESCAPE_SPECIAL) {
    - ret = escape_special(c, &p, &osz);
    - if (ret < 0)
    - break;
    - if (ret > 0)
    - continue;
    - }
    -
    - if (flags & ESCAPE_NULL) {
    - ret = escape_null(c, &p, &osz);
    - if (ret < 0)
    - break;
    - if (ret > 0)
    - continue;
    - }
    + if (flags & ESCAPE_SPACE && escape_space(c, &p, end))
    + continue;
    +
    + if (flags & ESCAPE_SPECIAL && escape_special(c, &p, end))
    + continue;
    +
    + if (flags & ESCAPE_NULL && escape_null(c, &p, end))
    + continue;

    /* ESCAPE_OCTAL and ESCAPE_HEX always go last */
    - if (flags & ESCAPE_OCTAL) {
    - ret = escape_octal(c, &p, &osz);
    - if (ret < 0)
    - break;
    + if (flags & ESCAPE_OCTAL && escape_octal(c, &p, end))
    continue;
    - }
    - if (flags & ESCAPE_HEX) {
    - ret = escape_hex(c, &p, &osz);
    - if (ret < 0)
    - break;
    +
    + if (flags & ESCAPE_HEX && escape_hex(c, &p, end))
    continue;
    - }
    }

    - ret = escape_passthrough(c, &p, &osz);
    - if (ret < 0)
    - break;
    + escape_passthrough(c, &p, end);
    + }
    + if (p > end) {
    + *dst = end;
    + return -ENOMEM;
    }

    + ret = p - *dst;
    *dst = p;
    -
    - if (ret < 0)
    - return ret;
    -
    - return p - out;
    + return ret;
    }
    EXPORT_SYMBOL(string_escape_mem);
    --
    2.1.3


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