TranscodingStreams.jl/src/transcode.jl at 93c28d42d4789bcb232a5614746d285533034bdf · JuliaIO/TranscodingStreams.jl · GitHub

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
# Transcode
# =========

"""
    transcode(
        ::Type{C},
        data::Union{Vector{UInt8},Base.CodeUnits{UInt8}},
    )::Vector{UInt8} where {C<:Codec}

Transcode `data` by applying a codec `C()`.

Note that this method does allocation and deallocation of `C()` in every call,
which is handy but less efficient when transcoding a number of objects.
`transcode(codec, data)` is a recommended method in terms of performance.

Examples
--------

```julia
julia> using CodecZlib

julia> data = b"abracadabra";

julia> compressed = transcode(ZlibCompressor, data);

julia> decompressed = transcode(ZlibDecompressor, compressed);

julia> String(decompressed)
"abracadabra"

```
"""
function Base.transcode(::Type{C}, args...) where {C<:Codec}
    codec = C()
    initialize(codec)
    try
        return transcode(codec, args...)
    finally
        finalize(codec)
    end
end

_default_output_buffer(codec, input) = Buffer(
    initial_output_size(
        codec,
        buffermem(input)
    )
)

"""
    transcode(
        codec::Codec,
        data::Union{Vector{UInt8},Base.CodeUnits{UInt8},Buffer},
        [output::Union{Vector{UInt8},Base.CodeUnits{UInt8},Buffer}],
    )::Vector{UInt8}

Transcode `data` by applying `codec`.

If `output` is unspecified, then this method will allocate it.

Note that this method does not initialize or finalize `codec`. This is
efficient when you transcode a number of pieces of data, but you need to call
[`TranscodingStreams.initialize`](@ref) and
[`TranscodingStreams.finalize`](@ref) explicitly.

Examples
--------

```julia
julia> using CodecZlib

julia> data = b"abracadabra";

julia> codec = ZlibCompressor();

julia> TranscodingStreams.initialize(codec)

julia> compressed = Vector{UInt8}()

julia> transcode(codec, data, compressed);

julia> TranscodingStreams.finalize(codec)

julia> codec = ZlibDecompressor();

julia> TranscodingStreams.initialize(codec)

julia> decompressed = transcode(codec, compressed);

julia> TranscodingStreams.finalize(codec)

julia> String(decompressed)
"abracadabra"

```
"""
function Base.transcode(
    codec::Codec,
    input::Buffer,
    output::Union{Buffer,Nothing} = nothing,
)
    output = (output === nothing ? _default_output_buffer(codec, input) : initbufer!(output))
    transcode!(output, codec, input)
end

"""
    transcode!(output::Buffer, codec::Codec, input::Buffer)

Transcode `input` by applying `codec` and storing the results in `output`.
Note that this method does not initialize or finalize `codec`. This is
efficient when you transcode a number of pieces of data, but you need to call
[`TranscodingStreams.initialize`](@ref) and
[`TranscodingStreams.finalize`](@ref) explicitly.
"""
function transcode!(
    output::Buffer,
    codec::Codec,
    input::Buffer,
)
    error = Error()
    code = startproc(codec, :write, error)
    if code === :error
        @goto error
    end
    n = minoutsize(codec, buffermem(input))
    @label process
    makemargin!(output, n)
    Δin, Δout, code = process(codec, buffermem(input), marginmem(output), error)
    @debug(
        "called process()",
        code = code,
        input_size = buffersize(input),
        output_size = marginsize(output),
        input_delta = Δin,
        output_delta = Δout,
    )
    consumed!(input, Δin)
    supplied!(output, Δout)
    if code === :error
        @goto error
    elseif code === :end
        if buffersize(input) > 0
            if startproc(codec, :write, error) === :error
                @goto error
            end
            n = minoutsize(codec, buffermem(input))
            @goto process
        end
        resize!(output.data, output.marginpos - 1)
        return output.data
    else
        n = max(Δout, minoutsize(codec, buffermem(input)))
        @goto process
    end
    @label error
    if !haserror(error)
        set_default_error!(error)
    end
    throw(error[])
end

Base.transcode(codec::Codec, data::Buffer, output::ByteData) =
    transcode(codec, data, Buffer(output))

Base.transcode(codec::Codec, data::ByteData, args...) =
    transcode(codec, Buffer(data), args...)

# Return the initial output buffer size.
function initial_output_size(codec::Codec, input::Memory)
    return max(
        minoutsize(codec, input),
        expectedsize(codec, input),
        8,  # just in case where both minoutsize and expectedsize are foolish
    )
end