Re-added SliceReaderAt
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5e6eafef64
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1
TODO.txt
1
TODO.txt
@ -1,3 +1,4 @@
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Test State against both possible ReaderAt EOF behaviors
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Write Repeat tests
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Think about not requiring so much Pos() when making messages
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Rename Seq2 to Seq
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@ -116,6 +116,22 @@ type ReaderAt[T any] interface {
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ReadAt(p []T, off int64) (n int, err error)
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}
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type SliceReaderAt[T any] []T
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func (s SliceReaderAt[T]) ReadAt(dst []T, off int64) (n int, err error) {
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if off < 0 {
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return 0, errors.New("SliceReaderAt.ReadAt: negative offset")
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}
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if off >= int64(len(s)) {
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return 0, io.EOF
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}
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n = copy(dst, s[off:])
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if n < len(dst) {
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err = io.EOF
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}
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return n, err
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}
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func MakeState[In any](r ReaderAt[In]) State[In] {
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return State[In]{r: r}
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}
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@ -2,11 +2,13 @@ package gigaparsec_test
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import (
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"bytes"
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"cmp"
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"io"
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"testing"
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"git.codemonkeysoftware.net/b/gigaparsec"
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ptest "git.codemonkeysoftware.net/b/gigaparsec/test"
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"git.codemonkeysoftware.net/b/gigaparsec/test/generator"
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pgen "git.codemonkeysoftware.net/b/gigaparsec/test/generator"
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"github.com/shoenig/test"
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"github.com/shoenig/test/must"
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@ -102,3 +104,42 @@ func TestState(t *testing.T) {
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test.Zero(t, n)
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}))
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}
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func TestSliceReaderAt(t *testing.T) {
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const maxLen = 100
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t.Run("offset ≥ 0", rapid.MakeCheck(func(t *rapid.T) {
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src := rapid.SliceOfN(rapid.Byte(), 0, maxLen).Draw(t, "src")
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dst := generator.SliceOfNZero[byte](0, maxLen).Draw(t, "dst")
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offset := rapid.Int64Range(0, int64(len(src))+10).Draw(t, "offset")
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n, err := gigaparsec.SliceReaderAt[byte](src).ReadAt(dst, offset)
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switch cmp.Compare(len(src), int(offset)+len(dst)) {
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case -1:
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// Read overruns src.
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test.ErrorIs(t, err, io.EOF)
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test.EqOp(t, max(0, len(src)-int(offset)), n)
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case 0:
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// Read exactly reaches end of source.
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// io.ReaderAt spec allows error to be either io.EOF or nil.
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test.EqOp(t, len(dst), n)
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case 1:
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// Read ends before end of source.
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test.NoError(t, err)
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test.EqOp(t, len(dst), n)
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}
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if offset < int64(len(src)) {
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test.SliceEqOp(t, src[offset:offset+int64(n)], dst[:n])
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}
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}))
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t.Run("offset < 0", rapid.MakeCheck(func(t *rapid.T) {
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src := rapid.SliceOfN(rapid.Byte(), 0, maxLen).Draw(t, "src")
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dst := generator.SliceOfNZero[byte](0, maxLen).Draw(t, "dst")
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offset := rapid.Int64Max(-1).Draw(t, "offset")
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n, err := gigaparsec.SliceReaderAt[byte](src).ReadAt(dst, offset)
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test.Error(t, err)
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test.EqOp(t, 0, n)
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}))
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}
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