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3393c13c00
not doing so means we always unmask from offset 0, which means we might use the wrong index in the mask if we do, say, `read()=3` followed by another read: the second one would start from mask[0] instead of mask[3], producing raw unfiltered garbage.
22 lines
708 B
C
22 lines
708 B
C
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#include <caml/alloc.h>
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#include <caml/memory.h>
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#include <caml/mlvalues.h>
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CAMLprim value tiny_httpd_ws_apply_masking(value _mask_key, value _mask_offset, value _buf,
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value _offset, value _len) {
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CAMLparam5(_mask_key, _mask_offset, _buf, _offset, _len);
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char const *mask_key = String_val(_mask_key);
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char *buf = Bytes_val(_buf);
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intnat mask_offset = Int_val(_mask_offset);
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intnat offset = Int_val(_offset);
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intnat len = Int_val(_len);
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for (intnat i = 0; i < len; ++i) {
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unsigned char c = buf[offset + i];
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unsigned char c_m = mask_key[(i + mask_offset) & 0x3];
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buf[offset + i] = (unsigned char)(c ^ c_m);
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}
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CAMLreturn(Val_unit);
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}
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