After feedback in IRC, I will drop this idea, and try to go the kernel way, supporting endianess annotated structures with sparse rules checking.
https://lwn.net/Articles/205624/ The motivation is that it's really difficult to keep in sync all the format strings, and although there may be ways to deal with it, I rather prefer this other design. On Mon, Oct 5, 2015 at 10:25 AM Javier Domingo Cansino <javier...@gmail.com> wrote: > Hello, > > I have been asked for examples and use cases. Github repo has been updated. > > I do also have doubts on if it's worth it. If a library like this existed > I would be definitely using it, make conversions, does take care of > alignment, can manage unaligned data and endianness. etc. > > But I am not really sure if someone apart from me would find it > interesting (long time ago I haven't seen a protocol unaligned with > different endianess). > > Waiting for your feedback! > > /* > * Syntax for the function is as follows. > * %[p][n][a][lb][01r]{i,y,w,d,q,s} > * > * All the characters that don't follow this will be treated as raw chars > * to be written as they are. > * > * Data type > * * i - bit > * * y - byte > * * w - 2 byte word > * * d - 4 byte word > * * q - 8 byte word > * * s - string without termination (use strlen()+1 in quantity to null) > * > * Data value > * * 0 - fill the specified space with zeros > * * 1 - fill the specified space with ones > * * r - fill the specified space with random data > * > * String data type is not valid in this case. When quantity is also > * specified, use l/b to separate: %5b0 -> 5 bits of value 0 > * > * Endianess. No conversion by default > * * l - little endian > * * b - big endian > * > * Alignment. No alignment by default > * * a - align this to it's datatype > * bits are aligned to byte > * > * Quantity. One by default > * * n - number of same datatype (placed together) > * this denotes length of string, padded with 0 > * > * Pointer. Default everything is passed by value > * * p - specify that passed parameter is a pointer to value(s) > * > * Obviously, when quantity is specified, and datatype is not bits, p > * is required. > * > * Some examples: > * * %4lw - 4 little endian 2 byte word > * * %2i - 2 bits 'ab' from value b'000000ab' > * * %2bi - 2 bits 'ab' from value b'000000ba' > * * %2li - 2 bits 'ab' from value b'ab000000' > * * %5y > * > * Calling functions example: > * int32_t dw[]=[1,2,3,4] > * > * v = writebv("%lw%2i%ay%p4d", 2047, 3, 'n', dw); > * > * in a big endian computer > * // *v = 0xff07c06e00000001000000020000000300000004 > * > * struct my_data_t { > * uint16_t a; > * uint8_t b:2; > * uint8_t unused1:6; > * uint8_t c; > * uint32_t d[4]; > * } *my_data; > * char letter; > * > * // If we want to have all extracted from the blob > * my_data = readbv(v, "%lw%2i%ay%p4d"); > * > * // If we just want to extract the char > * readb(v, "%0w%2l0i%ay%4l0d", &letter); > * > * // We have aligned data, but if we removed the 'a' from %ay, we > * wouldn't have unaligned data and this would still work. > * > */ > > >
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