[PD-dev] strings

[Martin Peach]

Hans-Christoph Steiner wrote:
>
> The one problem I can think of here is that you can only have 19 bits 
> of precision in Pd's 32-bit t_float.  So having a length of 32 bits 
> would cause problems if trying to deal with string length using 
> t_floats. I could see this happening in a loop in Pd space, for example.
Yes, and it's also easier to limit strings to word (16-bit) lengths, 
while 8-bit is too short.
So a t_string would look like:
typedef struct _string /* pointer to a string */
{
   unsigned short s_length; /* length of string in bytes */
   unsigned char *s_data; /* pointer to 1st byte of string */
} t_string;

Martin


>
> .hc
>
> On Dec 16, 2006, at 5:12 PM, Martin Peach wrote:
>
>> I think it would be most efficient to have a string type be a length 
>> followed by that many unsigned chars, similar to a Pascal string but 
>> with the length being something like a 32-bit integer. It would not 
>> be added to pd's symbol list. The atom whose type was string would 
>> have to contain a pointer to the first byte of the string, and a 
>> length. Multibyte characters would just be counted as multiple 
>> characters when calculating the length, so the length would be the 
>> number of bytes in the string, not the number of characters.
>> It looks too easy to me...In m_pd.h, add:
>> A_STRING
>> to t_atomtype.
>> Add
>> t_string * w_string;
>> to  t_word.
>> Add the typedef:
>> typedef struct _string /* pointer to a string */
>> {
>>    unsigned long s_length; /* length of string in bytes */
>>    unsigned char *s_data; /* pointer to 1st byte of string */
>> } t_string;
>>
>> ...so a string atom would have a_type = A_STRING and a_w = 
>> a_w.w_string, which points to a t_string containing the length and a 
>> pointer to the string.
>>
>> If pd is otherwise able to handle atom types it doesn't know about 
>> (?), all the string manipulation objects could be built as externals.
>>
>> Martin
>>
>>
>>
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>
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