Re: [PATCH v3 0/7] lib: string: add functions to case-convert strings

[Markus Mayer]

On 9 July 2016 at 20:13, Chris Metcalf  wrote:
> On 7/8/2016 6:43 PM, Markus Mayer wrote:
>>
>> This series introduces a family of generic string case conversion
>> functions. This kind of functionality is needed in several places in
>> the kernel. Right now, everybody seems to be implementing their own
>> copy of this functionality.
>>
>> Based on the discussion of the previous version of this series[1] and
>> the use cases found in the kernel, it does look like having several
>> flavours of case conversion functions is beneficial. The use cases fall
>> into three categories:
>>  - copying a string and converting the case while specifying a
>>maximum length to mimic strlcpy()
>>  - copying a string and converting the case without specifying a
>>length to mimic strcpy()
>>  - converting the case of a string in-place (i.e. modifying the
>>string that was passed in)
>>
>> Consequently, I am proposing these new functions:
>>  void strlcpytoupper(char *dst, const char *src, size_t len);
>>  void strlcpytolower(char *dst, const char *src, size_t len);
>>  void strcpytoupper(char *dst, const char *src);
>>  void strcpytolower(char *dst, const char *src);
>>  void strtoupper(char *s);
>>  void strtolower(char *s);
>
>
> You may want to read the article here:
>
> https://lwn.net/Articles/659214/

I'll read that. Thanks.

> and follow up some of the discussion threads on LKML about the best
> semantics to advertise for the strlcpy/strscpy variants.  It might be
> helpful to return some kind of overflow/truncation error from your
> copy functions so people can error-check the result.

I am inclined to agree. However, everybody has been telling me that
these functions should be void. Originally they weren't.

Regards,
-Markus
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Re: [PATCH v3 1/7] lib: string: add functions to case-convert strings

[Markus Mayer]

On 9 July 2016 at 05:04, Luis de Bethencourt  wrote:
> On 08/07/16 23:43, Markus Mayer wrote:
>> Add a collection of generic functions to convert strings to lowercase
>> or uppercase.
>>
>> Changing the case of a string (with or without copying it first) seems
>> to be a recurring requirement in the kernel that is currently being
>> solved by several duplicated implementations doing the same thing. This
>> change aims at reducing this code duplication.
>>
>> The new functions are
>> void strlcpytoupper(char *dst, const char *src, size_t len);
>> void strlcpytolower(char *dst, const char *src, size_t len);
>> void strcpytoupper(char *dst, const char *src);
>> void strcpytolower(char *dst, const char *src);
>> void strtoupper(char *s);
>> void strtolower(char *s);
>>
>> The "str[l]cpyto*" versions of the function take a destination string
>> and a source string as arguments. The "strlcpyto*" versions additionally
>> take a length argument like strlcpy() itself. Lastly, the strto*
>> functions take a single string argument and modify the passed-in string.
>>
>> Like strlcpy(), and unlike strncpy(), the functions guarantee NULL
>> termination of the destination string.
>>
>> Signed-off-by: Markus Mayer 
>> ---
>>  include/linux/string.h | 40 
>>  lib/string.c   | 38 ++
>>  2 files changed, 78 insertions(+)
>>
>> diff --git a/include/linux/string.h b/include/linux/string.h
>> index 26b6f6a..36c9d14 100644
>> --- a/include/linux/string.h
>> +++ b/include/linux/string.h
>> @@ -116,6 +116,8 @@ extern void * memchr(const void *,int,__kernel_size_t);
>>  #endif
>>  void *memchr_inv(const void *s, int c, size_t n);
>>  char *strreplace(char *s, char old, char new);
>> +extern void strlcpytoupper(char *dst, const char *src, size_t len);
>> +extern void strlcpytolower(char *dst, const char *src, size_t len);
>>
>>  extern void kfree_const(const void *x);
>>
>> @@ -169,4 +171,42 @@ static inline const char *kbasename(const char *path)
>>   return tail ? tail + 1 : path;
>>  }
>>
>> +/**
>> + * strcpytoupper - Copy string and convert to uppercase.
>> + * @dst: The buffer to store the result.
>> + * @src: The string to convert to uppercase.
>> + */
>> +static inline void strcpytoupper(char *dst, const char *src)
>> +{
>> + strlcpytoupper(dst, src, -1);
>> +}
>> +
>
> Why not use SIZE_MAX instead of -1?

Sure. I'll change all four of them. Thanks.

>> +/**
>> + * strcpytolower - Copy string and convert to lowercase.
>> + * @dst: The buffer to store the result.
>> + * @src: The string to convert to lowercase.
>> + */
>> +static inline void strcpytolower(char *dst, const char *src)
>> +{
>> + strlcpytolower(dst, src, -1);
>> +}
>> +
>
> Same here, and the 2 below :)
>
> Thanks Markus,
> Luis
>
>> +/**
>> + * strtoupper - Convert string to uppercase.
>> + * @s: The string to operate on.
>> + */
>> +static inline void strtoupper(char *s)
>> +{
>> + strlcpytoupper(s, s, -1);
>> +}
>> +
>> +/**
>> + * strtolower - Convert string to lowercase.
>> + * @s: The string to operate on.
>> + */
>> +static inline void strtolower(char *s)
>> +{
>> + strlcpytolower(s, s, -1);
>> +}
>> +
>>  #endif /* _LINUX_STRING_H_ */
>> diff --git a/lib/string.c b/lib/string.c
>> index ed83562..fd8c427 100644
>> --- a/lib/string.c
>> +++ b/lib/string.c
>> @@ -952,3 +952,41 @@ char *strreplace(char *s, char old, char new)
>>   return s;
>>  }
>>  EXPORT_SYMBOL(strreplace);
>> +
>> +/**
>> + * strlcpytoupper - Copy a length-limited string and convert to uppercase.
>> + * @dst: The buffer to store the result.
>> + * @src: The string to convert to uppercase.
>> + * @len: Maximum string length. May be SIZE_MAX (-1) to set no limit.
>> + */
>> +void strlcpytoupper(char *dst, const char *src, size_t len)
>> +{
>> + size_t i;
>> +
>> + if (!len)
>> + return;
>> +
>> + for (i = 0; i < len && src[i]; ++i)
>> + dst[i] = toupper(src[i]);
>> + dst[i < len ? i : i - 1] = '\0';
>> +}
>> +EXPORT_SYMBOL(strlcpytoupper);
>> +
>> +/**
>> + * strlcpytolower - Copy a length-limited string and convert to lowercase.
>> + * @dst: The buffer to store the result.
>> + * @src: The string to convert to lowercase.
>> + * @len: Maximum string length. May be SIZE_MAX (-1) to set no limit.
>> + */
>> +void strlcpytolower(char *dst, const char *src, size_t len)
>> +{
>> + size_t i;
>> +
>> + if (!len)
>> + return;
>> +
>> + for (i = 0; i < len && src[i]; ++i)
>> + dst[i] = tolower(src[i]);
>> + dst[i < len ? i : i - 1] = '\0';
>> +}
>> +EXPORT_SYMBOL(strlcpytolower);
>>
>
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Re: [PATCH v3 1/7] lib: string: add functions to case-convert strings

[Luis de Bethencourt]

On 08/07/16 23:43, Markus Mayer wrote:
> Add a collection of generic functions to convert strings to lowercase
> or uppercase.
> 
> Changing the case of a string (with or without copying it first) seems
> to be a recurring requirement in the kernel that is currently being
> solved by several duplicated implementations doing the same thing. This
> change aims at reducing this code duplication.
> 
> The new functions are
> void strlcpytoupper(char *dst, const char *src, size_t len);
> void strlcpytolower(char *dst, const char *src, size_t len);
> void strcpytoupper(char *dst, const char *src);
> void strcpytolower(char *dst, const char *src);
> void strtoupper(char *s);
> void strtolower(char *s);
> 
> The "str[l]cpyto*" versions of the function take a destination string
> and a source string as arguments. The "strlcpyto*" versions additionally
> take a length argument like strlcpy() itself. Lastly, the strto*
> functions take a single string argument and modify the passed-in string.
> 
> Like strlcpy(), and unlike strncpy(), the functions guarantee NULL
> termination of the destination string.
> 
> Signed-off-by: Markus Mayer 
> ---
>  include/linux/string.h | 40 
>  lib/string.c   | 38 ++
>  2 files changed, 78 insertions(+)
> 
> diff --git a/include/linux/string.h b/include/linux/string.h
> index 26b6f6a..36c9d14 100644
> --- a/include/linux/string.h
> +++ b/include/linux/string.h
> @@ -116,6 +116,8 @@ extern void * memchr(const void *,int,__kernel_size_t);
>  #endif
>  void *memchr_inv(const void *s, int c, size_t n);
>  char *strreplace(char *s, char old, char new);
> +extern void strlcpytoupper(char *dst, const char *src, size_t len);
> +extern void strlcpytolower(char *dst, const char *src, size_t len);
>  
>  extern void kfree_const(const void *x);
>  
> @@ -169,4 +171,42 @@ static inline const char *kbasename(const char *path)
>   return tail ? tail + 1 : path;
>  }
>  
> +/**
> + * strcpytoupper - Copy string and convert to uppercase.
> + * @dst: The buffer to store the result.
> + * @src: The string to convert to uppercase.
> + */
> +static inline void strcpytoupper(char *dst, const char *src)
> +{
> + strlcpytoupper(dst, src, -1);
> +}
> +

Why not use SIZE_MAX instead of -1?

> +/**
> + * strcpytolower - Copy string and convert to lowercase.
> + * @dst: The buffer to store the result.
> + * @src: The string to convert to lowercase.
> + */
> +static inline void strcpytolower(char *dst, const char *src)
> +{
> + strlcpytolower(dst, src, -1);
> +}
> +

Same here, and the 2 below :)

Thanks Markus,
Luis

> +/**
> + * strtoupper - Convert string to uppercase.
> + * @s: The string to operate on.
> + */
> +static inline void strtoupper(char *s)
> +{
> + strlcpytoupper(s, s, -1);
> +}
> +
> +/**
> + * strtolower - Convert string to lowercase.
> + * @s: The string to operate on.
> + */
> +static inline void strtolower(char *s)
> +{
> + strlcpytolower(s, s, -1);
> +}
> +
>  #endif /* _LINUX_STRING_H_ */
> diff --git a/lib/string.c b/lib/string.c
> index ed83562..fd8c427 100644
> --- a/lib/string.c
> +++ b/lib/string.c
> @@ -952,3 +952,41 @@ char *strreplace(char *s, char old, char new)
>   return s;
>  }
>  EXPORT_SYMBOL(strreplace);
> +
> +/**
> + * strlcpytoupper - Copy a length-limited string and convert to uppercase.
> + * @dst: The buffer to store the result.
> + * @src: The string to convert to uppercase.
> + * @len: Maximum string length. May be SIZE_MAX (-1) to set no limit.
> + */
> +void strlcpytoupper(char *dst, const char *src, size_t len)
> +{
> + size_t i;
> +
> + if (!len)
> + return;
> +
> + for (i = 0; i < len && src[i]; ++i)
> + dst[i] = toupper(src[i]);
> + dst[i < len ? i : i - 1] = '\0';
> +}
> +EXPORT_SYMBOL(strlcpytoupper);
> +
> +/**
> + * strlcpytolower - Copy a length-limited string and convert to lowercase.
> + * @dst: The buffer to store the result.
> + * @src: The string to convert to lowercase.
> + * @len: Maximum string length. May be SIZE_MAX (-1) to set no limit.
> + */
> +void strlcpytolower(char *dst, const char *src, size_t len)
> +{
> + size_t i;
> +
> + if (!len)
> + return;
> +
> + for (i = 0; i < len && src[i]; ++i)
> + dst[i] = tolower(src[i]);
> + dst[i < len ? i : i - 1] = '\0';
> +}
> +EXPORT_SYMBOL(strlcpytolower);
> 

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