mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-22 02:02:12 +00:00
80 lines
2.5 KiB
Go
80 lines
2.5 KiB
Go
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package binary
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import (
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"bytes"
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"fmt"
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"io"
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"github.com/tetratelabs/wazero/api"
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"github.com/tetratelabs/wazero/internal/leb128"
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"github.com/tetratelabs/wazero/internal/wasm"
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)
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// dataSegmentPrefix represents three types of data segments.
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//
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// https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/binary/modules.html#data-section
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type dataSegmentPrefix = uint32
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const (
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// dataSegmentPrefixActive is the prefix for the version 1.0 compatible data segment, which is classified as "active" in 2.0.
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dataSegmentPrefixActive dataSegmentPrefix = 0x0
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// dataSegmentPrefixPassive prefixes the "passive" data segment as in version 2.0 specification.
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dataSegmentPrefixPassive dataSegmentPrefix = 0x1
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// dataSegmentPrefixActiveWithMemoryIndex is the active prefix with memory index encoded which is defined for futur use as of 2.0.
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dataSegmentPrefixActiveWithMemoryIndex dataSegmentPrefix = 0x2
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)
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func decodeDataSegment(r *bytes.Reader, enabledFeatures api.CoreFeatures, ret *wasm.DataSegment) (err error) {
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dataSegmentPrefx, _, err := leb128.DecodeUint32(r)
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if err != nil {
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err = fmt.Errorf("read data segment prefix: %w", err)
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return
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}
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if dataSegmentPrefx != dataSegmentPrefixActive {
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if err = enabledFeatures.RequireEnabled(api.CoreFeatureBulkMemoryOperations); err != nil {
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err = fmt.Errorf("non-zero prefix for data segment is invalid as %w", err)
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return
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}
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}
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switch dataSegmentPrefx {
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case dataSegmentPrefixActive,
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dataSegmentPrefixActiveWithMemoryIndex:
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// Active data segment as in
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// https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/binary/modules.html#data-section
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if dataSegmentPrefx == 0x2 {
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d, _, err := leb128.DecodeUint32(r)
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if err != nil {
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return fmt.Errorf("read memory index: %v", err)
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} else if d != 0 {
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return fmt.Errorf("memory index must be zero but was %d", d)
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}
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}
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err = decodeConstantExpression(r, enabledFeatures, &ret.OffsetExpression)
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if err != nil {
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return fmt.Errorf("read offset expression: %v", err)
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}
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case dataSegmentPrefixPassive:
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// Passive data segment doesn't need const expr nor memory index encoded.
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// https://www.w3.org/TR/2022/WD-wasm-core-2-20220419/binary/modules.html#data-section
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ret.Passive = true
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default:
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err = fmt.Errorf("invalid data segment prefix: 0x%x", dataSegmentPrefx)
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return
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}
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vs, _, err := leb128.DecodeUint32(r)
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if err != nil {
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err = fmt.Errorf("get the size of vector: %v", err)
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return
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}
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ret.Init = make([]byte, vs)
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if _, err = io.ReadFull(r, ret.Init); err != nil {
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err = fmt.Errorf("read bytes for init: %v", err)
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}
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return
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}
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