koneu wrote:
> If anything, I would store the numbers as unsigned 64 bit LSB and change the
> read/write functions for MSB architectures.
Heyho,
max(uint32_t) = 4.294.967.296 is already way more than the proposed max of
999.999.999. I would even suggest uint16_t is enough. To store images larger
than 65536^2 (=16GiB with 4 bytes per pixel) is far enough in the future and
also the argument with the need for greater color depth applies. We could just
use htons and ntohs then:
spec
----
Bytes Description
9 ASCII string: "imagefile"
2 Width of the image stored in network byte order (big-endian)
2 Height of the image stored in network byte order (big-endian)
Then, (width*height) pixels arranged in height scanlines, where each pixel is
four bytes. Each byte represents red, green, blue, and alpha respectively.
This function reads an image:
char *
readimage(int fd, uint16_t *w, uint16_t *h)
{
char hdr[13];
char *data;
int len;
if (read(fd, hdr, 13) != 13 || strcmp(hdr, "imagefile"))
return NULL;
*w = ntohs(hdr[9]);
*h = ntohs(hdr[11]);
len = (*w) * (*h) * 4;
if (!(data = malloc(len)) || read(fd, data, len) != len) {
free(data);
return NULL;
}
return data;
}
This function writes an image:
int
writeimage(int fd, uint16_t w, uint16_t h, char *data)
{
uint16_t nw = htons(w);
uint16_t nh = htons(h);
return (write(fd, "imagefile", 9) == 9 &&
write(fd, &nw, 2) == 2 &&
write(fd, &nh, 2) == 2 &&
write(fd, data, w*h*4) == w*h*4);
}
We also avoid *printf and stdio.h.
--Markus
