Introduce TZAbbr

src/TimeZones.jl

@@ -55,6 +55,7 @@ include("indexable_generator.jl")
 
 include("class.jl")
 include("utcoffset.jl")
+include(joinpath("types", "tzabbr.jl"))
 include(joinpath("types", "timezone.jl"))
 include(joinpath("types", "fixedtimezone.jl"))
 include(joinpath("types", "variabletimezone.jl"))

src/types/tzabbr.jl

@@ -0,0 +1,89 @@
+const TZ_ABBR_MAX = 6
+
+"""
+    TimeZoneAbbr
+
+A three to six character string containing only ASCII alphanumerics, '+', and '-'.
+
+# https://data.iana.org/time-zones/theory.html#abbreviations
+"""
+struct TZAbbr <: AbstractString
+    chars::NTuple{TZ_ABBR_MAX, UInt8}
+end
+
+function TZAbbr(str::AbstractString)
+    if length(str) > TZ_ABBR_MAX
+        throw(ArgumentError("String length ($(length(str)) exceeds maximum abbreviation length ($TZ_ABBR_MAX)"))
+    end
+    chars = fill(tz_abbr_encode('\0'), TZ_ABBR_MAX)
+    i = 1
+    for c in str
+        chars[i] = tz_abbr_encode(c)
+        i += 1
+    end
+    return TZAbbr(Tuple(chars))
+end
+
+Base.iterate(a::TZAbbr) = iterate(a, 1)
+
+function Base.iterate(a::TZAbbr, i::Int)
+    i > TZ_ABBR_MAX && return nothing
+    c = tz_abbr_decode(a.chars[i])
+    c == '\0' && return nothing
+    return c, i + 1
+end
+
+function Base.ncodeunits(a::TZAbbr)
+    i = 0
+    for v in a.chars
+        c = tz_abbr_decode(v)
+        c == '\0' && return i
+        i += 1
+    end
+    return i
+end
+
+Base.codeunit(a::TZAbbr) = UInt8
+Base.codeunit(a::TZAbbr, i::Integer) = tz_abbr_decode(a.chars[i])
+Base.isvalid(a::TZAbbr, i::Integer) = tz_abbr_decode(a.chars[i]) != '\0'
+Base.sizeof(::TZAbbr) = TZ_ABBR_MAX
+
+function tz_abbr_decode(v::UInt8)
+    c = if v == UInt8(0)
+        '\0'
+    elseif v <= UInt8(26)  # A-Z
+        'A' + v - 1
+    elseif v <= UInt8(52)  # a-z
+        'a' + v - 27
+    elseif v <= UInt8(62)  # 0-9
+        '0' + v - 53
+    elseif v == UInt8(63)
+        '+'
+    elseif v == UInt8(64)
+        '-'
+    else
+        throw(ArgumentError("Decoding for $(repr(v)) is undefined and reserved for future use"))
+    end
+
+    return c
+end
+
+function tz_abbr_encode(c::Char)
+    v = if c == '\0'
+        UInt8(0)
+    elseif 'A' <= c <= 'Z'
+        UInt8(c - 'A' + 1)
+    elseif 'a' <= c <= 'z'
+        UInt8(c - 'a' + 27)
+    elseif '0' <= c <= '9'
+        UInt8(c - '0' + 53)
+    elseif c == '+'
+        UInt8(63)
+    elseif c == '-'
+        UInt8(64)
+    else
+        throw(ArgumentError("Character $(repr(c)) does not have a defined TZAbbr encoding"))
+    end
+
+    return v
+end

test/runtests.jl

@@ -52,6 +52,7 @@ include("helpers.jl")
     include(joinpath("tzdata", "compile.jl"))
     Sys.iswindows() && include(joinpath("winzone", "WindowsTimeZoneIDs.jl"))
     include("utcoffset.jl")
+    include(joinpath("types", "tzabbr.jl"))
     include(joinpath("types", "timezone.jl"))
     include(joinpath("types", "fixedtimezone.jl"))
     include(joinpath("types", "variabletimezone.jl"))

test/types/tzabbr.jl

@@ -0,0 +1,59 @@
+@testset "tz_abbr_encode" begin
+    @test tz_abbr_encode('\0') == UInt8(0)
+    @test tz_abbr_encode('A') == UInt8(1)
+    @test tz_abbr_encode('Z') == UInt8(26)
+    @test tz_abbr_encode('a') == UInt8(27)
+    @test tz_abbr_encode('z') == UInt8(52)
+    @test tz_abbr_encode('0') == UInt8(53)
+    @test tz_abbr_encode('+') == UInt8(63)
+    @test tz_abbr_encode('-') == UInt8(64)
+    @test_throws ArgumentError tz_abbr_encode('?')
+end
+
+@testset "tz_abbr_decode" begin
+    @test tz_abbr_decode(UInt8(0)) == '\0'
+    @test tz_abbr_decode(UInt8(1)) == 'A'
+    @test tz_abbr_decode(UInt8(26)) == 'Z'
+    @test tz_abbr_decode(UInt8(27)) == 'a'
+    @test tz_abbr_decode(UInt8(52)) == 'z'
+    @test tz_abbr_decode(UInt8(53)) == '0'
+    @test tz_abbr_decode(UInt8(63)) == '+'
+    @test tz_abbr_decode(UInt8(64)) == '-'
+    @test_throws ArgumentError tz_abbr_decode(UInt8(65))
+end
+
+@testset "TZAbbr" begin
+    @testset "iteration" begin
+        abbr = TZAbbr("X")
+
+        x = iterate(abbr)
+        @test x == ('X', 2)
+
+        x = iterate(abbr, 2)
+        @test x === nothing
+
+        @test collect(TZAbbr("UTC")) == ['U', 'T', 'C']
+    end
+
+    @testset "codeunits" begin
+        abbr = TZAbbr("UTC")
+
+        @test ncodeunits(abbr) == 3
+        @test codeunit(abbr) == UInt8
+        @test codeunit(abbr, 1) == 'U'
+    end
+
+    @testset "getindex" begin
+        abbr = TZAbbr("PDT")
+        @test abbr[1] == 'P'
+        @test abbr[2] == 'D'
+        @test abbr[3] == 'T'
+        @test_throws BoundsError abbr[4]
+    end
+
+    @testset "sizeof" begin
+        @test sizeof(TZAbbr("")) == 6
+        @test sizeof(TZAbbr("UTC")) == 6
+        @test sizeof(TZAbbr("FOOBAR")) == 6
+    end
+end