Retrieving binary data with XMLHttpRequest
Using XMLHttpRequest to fetch binary data from a HTTP source is “problematic”, as you can find with a simple websearch.
But what exactly means “problematic” in this context?
I gave it a try with Firefox and found out that every byte above 0x7f is translated into 0xfd. In other words: Plain old ASCII is left alone, everything above it results in a fixed value of 0xfd. Guess this has to do with the stream being interpreted as UTF-8 text…
A hex dump of a binary range [00 .. ff], retrieved through XMLHttpRequest:
joe$ od -t x1 -v xhrsweep.bin 0000000 00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f 0000020 10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f 0000040 20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f 0000060 30 31 32 33 34 35 36 37 38 39 3a 3b 3c 3d 3e 3f 0000100 40 41 42 43 44 45 46 47 48 49 4a 4b 4c 4d 4e 4f 0000120 50 51 52 53 54 55 56 57 58 59 5a 5b 5c 5d 5e 5f 0000140 60 61 62 63 64 65 66 67 68 69 6a 6b 6c 6d 6e 6f 0000160 70 71 72 73 74 75 76 77 78 79 7a 7b 7c 7d 7e 7f 0000200 fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0000220 fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0000240 fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0000260 fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0000300 fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0000320 fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0000340 fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0000360 fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0000400
