二郎IO：格式的二进制到十六进制 [英] Erlang io:formatting a binary to hex
问题描述
我可以格式化一个Erlang二进制？即，
Can I format an Erlang binary so that each byte is written in hex? I.e.,
> io:format(???, [<<255, 16>>]).
<<FF, 10>>
我没有看到一个明显的方式做到这一点在 IO：格式文档，但也许我只是缺少一个？转换二进制列出并分别格式化的元素效率太低。
I don't see an obvious way to do it in io:format documentation, but perhaps I am simply missing one? Converting a binary to list and formatting its elements separately is too inefficient.
推荐答案
没有，没有这样的格式化选项，但你可以这样做：
No, there is not such formating option but you can do something like:
io:format("<<~s>>~n", [[io_lib:format("~2.16.0B",[X]) || <<X:8>> <= <<255,16>> ]]).
有很多更快的解决方案，如果你需要的。
There is a lot faster solution if you need.
-module(bin_to_hex).
-compile([native, {hipe, [o3]}]).
-export([bin_to_hex/1]).
bin_to_hex(B) when is_binary(B) ->
bin_to_hex(B, <<>>).
-define(H(X), (hex(X)):16).
bin_to_hex(<<>>, Acc) -> Acc;
bin_to_hex(Bin, Acc) when byte_size(Bin) band 7 =:= 0 ->
bin_to_hex_(Bin, Acc);
bin_to_hex(<<X:8, Rest/binary>>, Acc) ->
bin_to_hex(Rest, <<Acc/binary, ?H(X)>>).
bin_to_hex_(<<>>, Acc) -> Acc;
bin_to_hex_(<<A:8, B:8, C:8, D:8, E:8, F:8, G:8, H:8, Rest/binary>>, Acc) ->
bin_to_hex_(
Rest,
<<Acc/binary,
?H(A), ?H(B), ?H(C), ?H(D), ?H(E), ?H(F), ?H(G), ?H(H)>>).
-compile({inline, [hex/1]}).
hex(X) ->
element(
X+1, {16#3030, 16#3031, 16#3032, 16#3033, 16#3034, 16#3035, 16#3036,
16#3037, 16#3038, 16#3039, 16#3041, 16#3042, 16#3043, 16#3044,
16#3045, 16#3046, 16#3130, 16#3131, 16#3132, 16#3133, 16#3134,
16#3135, 16#3136, 16#3137, 16#3138, 16#3139, 16#3141, 16#3142,
16#3143, 16#3144, 16#3145, 16#3146, 16#3230, 16#3231, 16#3232,
16#3233, 16#3234, 16#3235, 16#3236, 16#3237, 16#3238, 16#3239,
16#3241, 16#3242, 16#3243, 16#3244, 16#3245, 16#3246, 16#3330,
16#3331, 16#3332, 16#3333, 16#3334, 16#3335, 16#3336, 16#3337,
16#3338, 16#3339, 16#3341, 16#3342, 16#3343, 16#3344, 16#3345,
16#3346, 16#3430, 16#3431, 16#3432, 16#3433, 16#3434, 16#3435,
16#3436, 16#3437, 16#3438, 16#3439, 16#3441, 16#3442, 16#3443,
16#3444, 16#3445, 16#3446, 16#3530, 16#3531, 16#3532, 16#3533,
16#3534, 16#3535, 16#3536, 16#3537, 16#3538, 16#3539, 16#3541,
16#3542, 16#3543, 16#3544, 16#3545, 16#3546, 16#3630, 16#3631,
16#3632, 16#3633, 16#3634, 16#3635, 16#3636, 16#3637, 16#3638,
16#3639, 16#3641, 16#3642, 16#3643, 16#3644, 16#3645, 16#3646,
16#3730, 16#3731, 16#3732, 16#3733, 16#3734, 16#3735, 16#3736,
16#3737, 16#3738, 16#3739, 16#3741, 16#3742, 16#3743, 16#3744,
16#3745, 16#3746, 16#3830, 16#3831, 16#3832, 16#3833, 16#3834,
16#3835, 16#3836, 16#3837, 16#3838, 16#3839, 16#3841, 16#3842,
16#3843, 16#3844, 16#3845, 16#3846, 16#3930, 16#3931, 16#3932,
16#3933, 16#3934, 16#3935, 16#3936, 16#3937, 16#3938, 16#3939,
16#3941, 16#3942, 16#3943, 16#3944, 16#3945, 16#3946, 16#4130,
16#4131, 16#4132, 16#4133, 16#4134, 16#4135, 16#4136, 16#4137,
16#4138, 16#4139, 16#4141, 16#4142, 16#4143, 16#4144, 16#4145,
16#4146, 16#4230, 16#4231, 16#4232, 16#4233, 16#4234, 16#4235,
16#4236, 16#4237, 16#4238, 16#4239, 16#4241, 16#4242, 16#4243,
16#4244, 16#4245, 16#4246, 16#4330, 16#4331, 16#4332, 16#4333,
16#4334, 16#4335, 16#4336, 16#4337, 16#4338, 16#4339, 16#4341,
16#4342, 16#4343, 16#4344, 16#4345, 16#4346, 16#4430, 16#4431,
16#4432, 16#4433, 16#4434, 16#4435, 16#4436, 16#4437, 16#4438,
16#4439, 16#4441, 16#4442, 16#4443, 16#4444, 16#4445, 16#4446,
16#4530, 16#4531, 16#4532, 16#4533, 16#4534, 16#4535, 16#4536,
16#4537, 16#4538, 16#4539, 16#4541, 16#4542, 16#4543, 16#4544,
16#4545, 16#4546, 16#4630, 16#4631, 16#4632, 16#4633, 16#4634,
16#4635, 16#4636, 16#4637, 16#4638, 16#4639, 16#4641, 16#4642,
16#4643, 16#4644, 16#4645, 16#4646}).
这当10MB块测试@ 2.40GHz的矿山上的i5笔记本CPU中号520执行90MB /秒。不过，优化被带到极端。它也可以做97MB，如果使用16位的查找，但它是疯了，太长时间在这里发表。
Which performs 90MB/s on mine notebook i5 CPU M 520 @ 2.40GHz when tested on 10MB chunks. But optimization was brought to the extreme there. It can also do 97MB if using 16bit lookup but it is crazy and too long to post here.
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