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Subject[PATCH v4 02/34] lib/string_helpers: Convert string_escape_mem() to printbuf
Date
Like the upcoming vsprintf.c conversion, this converts string_escape_mem
to prt_escaped_string(), which uses and outputs to a printbuf, and makes
string_escape_mem() a smaller wrapper to support existing users.

The new printbuf helpers greatly simplify the code.

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
---
include/linux/string_helpers.h | 4 +
lib/string_helpers.c | 217 ++++++++++++++++++---------------
2 files changed, 126 insertions(+), 95 deletions(-)

diff --git a/include/linux/string_helpers.h b/include/linux/string_helpers.h
index 4d72258d42..67de398944 100644
--- a/include/linux/string_helpers.h
+++ b/include/linux/string_helpers.h
@@ -10,6 +10,7 @@
struct device;
struct file;
struct task_struct;
+struct printbuf;

/* Descriptions of the types of units to
* print in */
@@ -62,6 +63,8 @@ static inline int string_unescape_any_inplace(char *buf)

#define ESCAPE_ALL_MASK GENMASK(8, 0)

+void prt_escaped_string(struct printbuf *out, const char *src, size_t isz,
+ unsigned int flags, const char *only);
int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
unsigned int flags, const char *only);

@@ -71,6 +74,7 @@ static inline int string_escape_mem_any_np(const char *src, size_t isz,
return string_escape_mem(src, isz, dst, osz, ESCAPE_ANY_NP, only);
}

+
static inline int string_escape_str(const char *src, char *dst, size_t sz,
unsigned int flags, const char *only)
{
diff --git a/lib/string_helpers.c b/lib/string_helpers.c
index 4f877e9551..167c31f377 100644
--- a/lib/string_helpers.c
+++ b/lib/string_helpers.c
@@ -15,6 +15,7 @@
#include <linux/fs.h>
#include <linux/limits.h>
#include <linux/mm.h>
+#include <linux/printbuf.h>
#include <linux/slab.h>
#include <linux/string.h>
#include <linux/string_helpers.h>
@@ -301,19 +302,14 @@ int string_unescape(char *src, char *dst, size_t size, unsigned int flags)
}
EXPORT_SYMBOL(string_unescape);

-static bool escape_passthrough(unsigned char c, char **dst, char *end)
+static bool escape_passthrough(struct printbuf *out, unsigned char c)
{
- char *out = *dst;
-
- if (out < end)
- *out = c;
- *dst = out + 1;
+ prt_char(out, c);
return true;
}

-static bool escape_space(unsigned char c, char **dst, char *end)
+static bool escape_space(struct printbuf *out, unsigned char c)
{
- char *out = *dst;
unsigned char to;

switch (c) {
@@ -336,20 +332,13 @@ static bool escape_space(unsigned char c, char **dst, char *end)
return false;
}

- if (out < end)
- *out = '\\';
- ++out;
- if (out < end)
- *out = to;
- ++out;
-
- *dst = out;
+ prt_char(out, '\\');
+ prt_char(out, to);
return true;
}

-static bool escape_special(unsigned char c, char **dst, char *end)
+static bool escape_special(struct printbuf *out, unsigned char c)
{
- char *out = *dst;
unsigned char to;

switch (c) {
@@ -369,83 +358,43 @@ static bool escape_special(unsigned char c, char **dst, char *end)
return false;
}

- if (out < end)
- *out = '\\';
- ++out;
- if (out < end)
- *out = to;
- ++out;
-
- *dst = out;
+ prt_char(out, '\\');
+ prt_char(out, to);
return true;
}

-static bool escape_null(unsigned char c, char **dst, char *end)
+static bool escape_null(struct printbuf *out, unsigned char c)
{
- char *out = *dst;
-
if (c)
return false;

- if (out < end)
- *out = '\\';
- ++out;
- if (out < end)
- *out = '0';
- ++out;
-
- *dst = out;
+ prt_char(out, '\\');
+ prt_char(out, '0');
return true;
}

-static bool escape_octal(unsigned char c, char **dst, char *end)
+static bool escape_octal(struct printbuf *out, unsigned char c)
{
- char *out = *dst;
-
- if (out < end)
- *out = '\\';
- ++out;
- if (out < end)
- *out = ((c >> 6) & 0x07) + '0';
- ++out;
- if (out < end)
- *out = ((c >> 3) & 0x07) + '0';
- ++out;
- if (out < end)
- *out = ((c >> 0) & 0x07) + '0';
- ++out;
-
- *dst = out;
+ prt_char(out, '\\');
+ prt_char(out, ((c >> 6) & 0x07) + '0');
+ prt_char(out, ((c >> 3) & 0x07) + '0');
+ prt_char(out, ((c >> 0) & 0x07) + '0');
return true;
}

-static bool escape_hex(unsigned char c, char **dst, char *end)
+static bool escape_hex(struct printbuf *out, unsigned char c)
{
- char *out = *dst;
-
- if (out < end)
- *out = '\\';
- ++out;
- if (out < end)
- *out = 'x';
- ++out;
- if (out < end)
- *out = hex_asc_hi(c);
- ++out;
- if (out < end)
- *out = hex_asc_lo(c);
- ++out;
-
- *dst = out;
+ prt_char(out, '\\');
+ prt_char(out, 'x');
+ prt_hex_byte(out, c);
return true;
}

/**
- * string_escape_mem - quote characters in the given memory buffer
+ * prt_escaped_string - quote characters in the given memory buffer
+ * @out: printbuf to output to (escaped)
* @src: source buffer (unescaped)
* @isz: source buffer size
- * @dst: destination buffer (escaped)
- * @osz: destination buffer size
* @flags: combination of the flags
* @only: NULL-terminated string containing characters used to limit
* the selected escape class. If characters are included in @only
@@ -510,18 +459,11 @@ static bool escape_hex(unsigned char c, char **dst, char *end)
* or %ESCAPE_HEX, because they cover most of the other character classes.
* %ESCAPE_NAP can utilize %ESCAPE_SPACE or %ESCAPE_SPECIAL in addition to
* the above.
- *
- * Return:
- * The total size of the escaped output that would be generated for
- * the given input and flags. To check whether the output was
- * truncated, compare the return value to osz. There is room left in
- * dst for a '\0' terminator if and only if ret < osz.
*/
-int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
- unsigned int flags, const char *only)
+void prt_escaped_string(struct printbuf *out,
+ const char *src, size_t isz,
+ unsigned int flags, const char *only)
{
- char *p = dst;
- char *end = p + osz;
bool is_dict = only && *only;
bool is_append = flags & ESCAPE_APPEND;

@@ -549,41 +491,126 @@ int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
* %ESCAPE_NA cases.
*/
if (!(is_append || in_dict) && is_dict &&
- escape_passthrough(c, &p, end))
+ escape_passthrough(out, c))
continue;

if (!(is_append && in_dict) && isascii(c) && isprint(c) &&
- flags & ESCAPE_NAP && escape_passthrough(c, &p, end))
+ flags & ESCAPE_NAP && escape_passthrough(out, c))
continue;

if (!(is_append && in_dict) && isprint(c) &&
- flags & ESCAPE_NP && escape_passthrough(c, &p, end))
+ flags & ESCAPE_NP && escape_passthrough(out, c))
continue;

if (!(is_append && in_dict) && isascii(c) &&
- flags & ESCAPE_NA && escape_passthrough(c, &p, end))
+ flags & ESCAPE_NA && escape_passthrough(out, c))
continue;

- if (flags & ESCAPE_SPACE && escape_space(c, &p, end))
+ if (flags & ESCAPE_SPACE && escape_space(out, c))
continue;

- if (flags & ESCAPE_SPECIAL && escape_special(c, &p, end))
+ if (flags & ESCAPE_SPECIAL && escape_special(out, c))
continue;

- if (flags & ESCAPE_NULL && escape_null(c, &p, end))
+ if (flags & ESCAPE_NULL && escape_null(out, c))
continue;

/* ESCAPE_OCTAL and ESCAPE_HEX always go last */
- if (flags & ESCAPE_OCTAL && escape_octal(c, &p, end))
+ if (flags & ESCAPE_OCTAL && escape_octal(out, c))
continue;

- if (flags & ESCAPE_HEX && escape_hex(c, &p, end))
+ if (flags & ESCAPE_HEX && escape_hex(out, c))
continue;

- escape_passthrough(c, &p, end);
+ escape_passthrough(out, c);
}
+}
+EXPORT_SYMBOL(prt_escaped_string);
+
+/**
+ * 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
+ * @only: NULL-terminated string containing characters used to limit
+ * the selected escape class. If characters are included in @only
+ * that would not normally be escaped by the classes selected
+ * in @flags, they will be copied to @dst unescaped.
+ *
+ * Description:
+ * The process of escaping byte buffer includes several parts. They are applied
+ * in the following sequence.
+ *
+ * 1. The character is not matched to the one from @only string and thus
+ * must go as-is to the output.
+ * 2. The character is matched to the printable and ASCII classes, if asked,
+ * and in case of match it passes through to the output.
+ * 3. The character is matched to the printable or ASCII class, if asked,
+ * and in case of match it passes through to the output.
+ * 4. 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. The supported flags are::
+ *
+ * %ESCAPE_SPACE: (special white space, not space itself)
+ * '\f' - form feed
+ * '\n' - new line
+ * '\r' - carriage return
+ * '\t' - horizontal tab
+ * '\v' - vertical tab
+ * %ESCAPE_SPECIAL:
+ * '\"' - double quote
+ * '\\' - 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)
+ * %ESCAPE_NA:
+ * escape only non-ascii characters, checked by isascii()
+ * %ESCAPE_NAP:
+ * escape only non-printable or non-ascii characters
+ * %ESCAPE_APPEND:
+ * append characters from @only to be escaped by the given classes
+ *
+ * %ESCAPE_APPEND would help to pass additional characters to the escaped, when
+ * one of %ESCAPE_NP, %ESCAPE_NA, or %ESCAPE_NAP is provided.
+ *
+ * One notable caveat, the %ESCAPE_NAP, %ESCAPE_NP and %ESCAPE_NA have the
+ * higher priority than the rest of the flags (%ESCAPE_NAP is the highest).
+ * It doesn't make much sense to use either of them without %ESCAPE_OCTAL
+ * or %ESCAPE_HEX, because they cover most of the other character classes.
+ * %ESCAPE_NAP can utilize %ESCAPE_SPACE or %ESCAPE_SPECIAL in addition to
+ * the above.
+ *
+ * Return:
+ * The total size of the escaped output that would be generated for
+ * the given input and flags. To check whether the output was
+ * truncated, compare the return value to osz. There is room left in
+ * dst for a '\0' terminator if and only if ret < osz.
+ */
+int string_escape_mem(const char *src, size_t isz, char *dst, size_t osz,
+ unsigned int flags, const char *only)
+{
+ struct printbuf out = PRINTBUF_EXTERN(dst, osz);

- return p - dst;
+ prt_escaped_string(&out, src, isz, flags, only);
+ return out.pos;
}
EXPORT_SYMBOL(string_escape_mem);

--
2.36.1
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