diff options
Diffstat (limited to 'lib/string_helpers.c')
| -rw-r--r-- | lib/string_helpers.c | 274 |
1 files changed, 274 insertions, 0 deletions
diff --git a/lib/string_helpers.c b/lib/string_helpers.c index 74ec60469640..58b78ba57439 100644 --- a/lib/string_helpers.c +++ b/lib/string_helpers.c @@ -8,6 +8,8 @@ #include <linux/math64.h> #include <linux/export.h> #include <linux/ctype.h> +#include <linux/errno.h> +#include <linux/string.h> #include <linux/string_helpers.h> /** @@ -240,3 +242,275 @@ int string_unescape(char *src, char *dst, size_t size, unsigned int flags) return out - dst; } EXPORT_SYMBOL(string_unescape); + +static int escape_passthrough(unsigned char c, char **dst, size_t *osz) +{ + char *out = *dst; + + if (*osz < 1) + return -ENOMEM; + + *out++ = c; + + *dst = out; + *osz -= 1; + + return 1; +} + +static int escape_space(unsigned char c, char **dst, size_t *osz) +{ + char *out = *dst; + unsigned char to; + + if (*osz < 2) + return -ENOMEM; + + switch (c) { + case '\n': + to = 'n'; + break; + case '\r': + to = 'r'; + break; + case '\t': + to = 't'; + break; + case '\v': + to = 'v'; + break; + case '\f': + to = 'f'; + break; + default: + return 0; + } + + *out++ = '\\'; + *out++ = to; + + *dst = out; + *osz -= 2; + + return 1; +} + +static int escape_special(unsigned char c, char **dst, size_t *osz) +{ + char *out = *dst; + unsigned char to; + + if (*osz < 2) + return -ENOMEM; + + switch (c) { + case '\\': + to = '\\'; + break; + case '\a': + to = 'a'; + break; + case '\e': + to = 'e'; + break; + default: + return 0; + } + + *out++ = '\\'; + *out++ = to; + + *dst = out; + *osz -= 2; + + return 1; +} + +static int escape_null(unsigned char c, char **dst, size_t *osz) +{ + char *out = *dst; + + if (*osz < 2) + return -ENOMEM; + + if (c) + return 0; + + *out++ = '\\'; + *out++ = '0'; + + *dst = out; + *osz -= 2; + + return 1; +} + +static int escape_octal(unsigned char c, char **dst, size_t *osz) +{ + char *out = *dst; + + if (*osz < 4) + return -ENOMEM; + + *out++ = '\\'; + *out++ = ((c >> 6) & 0x07) + '0'; + *out++ = ((c >> 3) & 0x07) + '0'; + *out++ = ((c >> 0) & 0x07) + '0'; + + *dst = out; + *osz -= 4; + + return 1; +} + +static int escape_hex(unsigned char c, char **dst, size_t *osz) +{ + 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; + + return 1; +} + +/** + * string_escape_mem - quote characters in the given memory buffer + * @src: source buffer (unescaped) + * @isz: source buffer size + * @dst: destination buffer (escaped) + * @osz: destination buffer size + * @flags: combination of the flags (bitwise OR): + * %ESCAPE_SPACE: + * '\f' - form feed + * '\n' - new line + * '\r' - carriage return + * '\t' - horizontal tab + * '\v' - vertical tab + * %ESCAPE_SPECIAL: + * '\\' - backslash + * '\a' - alert (BEL) + * '\e' - escape + * %ESCAPE_NULL: + * '\0' - null + * %ESCAPE_OCTAL: + * '\NNN' - byte with octal value NNN (3 digits) + * %ESCAPE_ANY: + * all previous together + * %ESCAPE_NP: + * escape only non-printable characters (checked by isprint) + * %ESCAPE_ANY_NP: + * all previous together + * %ESCAPE_HEX: + * '\xHH' - byte with hexadecimal value HH (2 digits) + * @esc: NULL-terminated string of characters any of which, if found in + * the source, has to be escaped + * + * Description: + * The process of escaping byte buffer includes several parts. They are applied + * in the following sequence. + * 1. The character is matched to the printable class, if asked, and in + * case of match it passes through to the output. + * 2. The character is not matched to the one from @esc string and thus + * must go as is to the output. + * 3. The character is checked if it falls into the class given by @flags. + * %ESCAPE_OCTAL and %ESCAPE_HEX are going last since they cover any + * character. Note that they actually can't go together, otherwise + * %ESCAPE_HEX will be ignored. + * + * Caller must provide valid source and destination pointers. Be aware that + * destination buffer will not be NULL-terminated, thus caller have to append + * it if needs. + * + * Return: + * The amount of the characters processed to the destination buffer, or + * %-ENOMEM if the size of buffer is not enough to put an escaped character is + * returned. + * + * Even in the case of error @dst pointer will be updated to point to the byte + * after the last processed character. + */ +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; + bool is_dict = esc && *esc; + int ret = 0; + + while (isz--) { + unsigned char c = *src++; + + /* + * Apply rules in the following sequence: + * - the character is printable, when @flags has + * %ESCAPE_NP bit set + * - the @esc string is supplied and does not contain a + * character under question + * - the character doesn't fall into a class of symbols + * defined by given @flags + * In these cases we just pass through a character to the + * output buffer. + */ + if ((flags & ESCAPE_NP && isprint(c)) || + (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; + } + + /* ESCAPE_OCTAL and ESCAPE_HEX always go last */ + if (flags & ESCAPE_OCTAL) { + ret = escape_octal(c, &p, &osz); + if (ret < 0) + break; + continue; + } + if (flags & ESCAPE_HEX) { + ret = escape_hex(c, &p, &osz); + if (ret < 0) + break; + continue; + } + } + + ret = escape_passthrough(c, &p, &osz); + if (ret < 0) + break; + } + + *dst = p; + + if (ret < 0) + return ret; + + return p - out; +} +EXPORT_SYMBOL(string_escape_mem); |