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271
dynamodb/key_codec.odin
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271
dynamodb/key_codec.odin
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package dynamodb
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import "core:bytes"
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// Entity type prefix bytes for namespacing
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Entity_Type :: enum u8 {
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Meta = 0x01, // Table metadata
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Data = 0x02, // Item data
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GSI = 0x03, // Global secondary index
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LSI = 0x04, // Local secondary index
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}
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// Decode a varint length prefix from a byte slice.
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// Reads starting at data[offset^] and advances offset^ past the varint on success.
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decode_varint :: proc(data: []byte, offset: ^int) -> (value: int, ok: bool) {
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i := offset^
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if i < 0 || i >= len(data) {
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return 0, false
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}
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u: u64 = 0
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shift: u32 = 0
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for {
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if i >= len(data) {
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return 0, false // truncated
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}
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b := data[i]
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i += 1
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u |= u64(b & 0x7F) << shift
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if (b & 0x80) == 0 {
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break
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}
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shift += 7
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if shift >= 64 {
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return 0, false // malformed / overflow
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}
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}
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// ensure it fits in int on this platform
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max_int := int((~uint(0)) >> 1)
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if u > u64(max_int) {
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return 0, false
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}
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offset^ = i
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return int(u), true
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}
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// Build metadata key: [meta][table_name]
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build_meta_key :: proc(table_name: string) -> []byte {
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buf: bytes.Buffer
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bytes.buffer_init_allocator(&buf, 0, 256, context.allocator)
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// Write entity type
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bytes.buffer_write_byte(&buf, u8(Entity_Type.Meta))
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// Write table name with length prefix
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encode_varint(&buf, len(table_name))
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bytes.buffer_write_string(&buf, table_name)
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return bytes.buffer_to_bytes(&buf)
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}
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// Build data key: [data][table_name][pk_value][sk_value?]
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build_data_key :: proc(table_name: string, pk_value: []byte, sk_value: Maybe([]byte)) -> []byte {
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buf: bytes.Buffer
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bytes.buffer_init_allocator(&buf, 0, 512, context.allocator)
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// Write entity type
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bytes.buffer_write_byte(&buf, u8(Entity_Type.Data))
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// Write table name
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encode_varint(&buf, len(table_name))
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bytes.buffer_write_string(&buf, table_name)
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// Write partition key
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encode_varint(&buf, len(pk_value))
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bytes.buffer_write(&buf, pk_value)
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// Write sort key if present
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if sk, ok := sk_value.?; ok {
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encode_varint(&buf, len(sk))
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bytes.buffer_write(&buf, sk)
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}
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return bytes.buffer_to_bytes(&buf)
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}
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// Build table prefix for scanning: [data][table_name]
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build_table_prefix :: proc(table_name: string) -> []byte {
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buf: bytes.Buffer
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bytes.buffer_init_allocator(&buf, 0, 256, context.allocator)
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// Write entity type
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bytes.buffer_write_byte(&buf, u8(Entity_Type.Data))
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// Write table name
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encode_varint(&buf, len(table_name))
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bytes.buffer_write_string(&buf, table_name)
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return bytes.buffer_to_bytes(&buf)
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}
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// Build partition prefix for querying: [data][table_name][pk_value]
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build_partition_prefix :: proc(table_name: string, pk_value: []byte) -> []byte {
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buf: bytes.Buffer
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bytes.buffer_init_allocator(&buf, 0, 512, context.allocator)
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// Write entity type
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bytes.buffer_write_byte(&buf, u8(Entity_Type.Data))
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// Write table name
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encode_varint(&buf, len(table_name))
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bytes.buffer_write_string(&buf, table_name)
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// Write partition key
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encode_varint(&buf, len(pk_value))
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bytes.buffer_write(&buf, pk_value)
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return bytes.buffer_to_bytes(&buf)
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}
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// Build GSI key: [gsi][table_name][index_name][gsi_pk][gsi_sk?]
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build_gsi_key :: proc(table_name: string, index_name: string, gsi_pk: []byte, gsi_sk: Maybe([]byte)) -> []byte {
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buf: bytes.Buffer
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bytes.buffer_init_allocator(&buf, 0, 512, context.allocator)
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// Write entity type
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bytes.buffer_write_byte(&buf, u8(Entity_Type.GSI))
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// Write table name
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encode_varint(&buf, len(table_name))
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bytes.buffer_write_string(&buf, table_name)
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// Write index name
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encode_varint(&buf, len(index_name))
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bytes.buffer_write_string(&buf, index_name)
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// Write GSI partition key
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encode_varint(&buf, len(gsi_pk))
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bytes.buffer_write(&buf, gsi_pk)
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// Write GSI sort key if present
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if sk, ok := gsi_sk.?; ok {
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encode_varint(&buf, len(sk))
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bytes.buffer_write(&buf, sk)
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}
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return bytes.buffer_to_bytes(&buf)
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}
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// Build LSI key: [lsi][table_name][index_name][pk][lsi_sk]
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build_lsi_key :: proc(table_name: string, index_name: string, pk: []byte, lsi_sk: []byte) -> []byte {
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buf: bytes.Buffer
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bytes.buffer_init_allocator(&buf, 0, 512, context.allocator)
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// Write entity type
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bytes.buffer_write_byte(&buf, u8(Entity_Type.LSI))
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// Write table name
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encode_varint(&buf, len(table_name))
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bytes.buffer_write_string(&buf, table_name)
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// Write index name
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encode_varint(&buf, len(index_name))
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bytes.buffer_write_string(&buf, index_name)
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// Write partition key
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encode_varint(&buf, len(pk))
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bytes.buffer_write(&buf, pk)
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// Write LSI sort key
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encode_varint(&buf, len(lsi_sk))
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bytes.buffer_write(&buf, lsi_sk)
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return bytes.buffer_to_bytes(&buf)
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}
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// Key decoder for reading binary keys
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Key_Decoder :: struct {
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data: []byte,
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pos: int,
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}
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decoder_read_entity_type :: proc(decoder: ^Key_Decoder) -> (Entity_Type, bool) {
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if decoder.pos >= len(decoder.data) {
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return .Meta, false
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}
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entity_type := Entity_Type(decoder.data[decoder.pos])
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decoder.pos += 1
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return entity_type, true
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}
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decoder_read_segment :: proc(decoder: ^Key_Decoder) -> (segment: []byte, ok: bool) {
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// Read length
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length := decode_varint(decoder.data, &decoder.pos) or_return
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// Read data
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if decoder.pos + length > len(decoder.data) {
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return nil, false
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}
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// Return slice (owned by caller via context.allocator)
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segment = make([]byte, length, context.allocator)
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copy(segment, decoder.data[decoder.pos:decoder.pos + length])
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decoder.pos += length
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return segment, true
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}
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decoder_read_segment_borrowed :: proc(decoder: ^Key_Decoder) -> (segment: []byte, ok: bool) {
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// Read length
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length := decode_varint(decoder.data, &decoder.pos) or_return
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// Return borrowed slice
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if decoder.pos + length > len(decoder.data) {
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return nil, false
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}
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segment = decoder.data[decoder.pos:decoder.pos + length]
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decoder.pos += length
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return segment, true
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}
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decoder_has_more :: proc(decoder: ^Key_Decoder) -> bool {
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return decoder.pos < len(decoder.data)
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}
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// Decode a data key back into components
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Decoded_Data_Key :: struct {
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table_name: string,
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pk_value: []byte,
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sk_value: Maybe([]byte),
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}
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decode_data_key :: proc(key: []byte) -> (result: Decoded_Data_Key, ok: bool) {
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decoder := Key_Decoder{data = key, pos = 0}
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// Read and verify entity type
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entity_type := decoder_read_entity_type(&decoder) or_return
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if entity_type != .Data {
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return {}, false
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}
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// Read table name
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table_name_bytes := decoder_read_segment(&decoder) or_return
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result.table_name = string(table_name_bytes)
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// Read partition key
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result.pk_value = decoder_read_segment(&decoder) or_return
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// Read sort key if present
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if decoder_has_more(&decoder) {
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sk := decoder_read_segment(&decoder) or_return
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result.sk_value = sk
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}
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return result, true
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}
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