tiny.sql.record

1const std = @import("std");23pub const Error = error{4    InvalidRecord,5    ValueTooLarge,6};78pub const Kind = enum {9    inline_value,10    overflow,11};1213pub const Overflow = struct {14    len: u64,15    first_page: u32,16};1718pub const inline_tag: u8 = 0;19pub const overflow_tag: u8 = 1;20pub const overflow_size: usize = 13;2122pub fn inlineSize(value: []const u8) Error!usize {23    if (value.len == std.math.maxInt(usize)) return error.ValueTooLarge;24    return value.len + 1;25}2627pub fn encodeInline(target: []u8, value: []const u8) Error![]const u8 {28    const len = try inlineSize(value);29    if (target.len < len) return error.ValueTooLarge;30    target[0] = inline_tag;31    @memcpy(target[1..][0..value.len], value);32    return target[0..len];33}3435pub fn encodeOverflow(target: *[overflow_size]u8, value: Overflow) Error![]const u8 {36    if (value.len == 0 or value.first_page == 0) return error.InvalidRecord;37    target[0] = overflow_tag;38    std.mem.writeInt(u64, target[1..][0..8], value.len, .big);39    std.mem.writeInt(u32, target[9..][0..4], value.first_page, .big);40    return target[0..];41}4243pub fn kind(bytes: []const u8) Error!Kind {44    if (bytes.len == 0) return error.InvalidRecord;45    return switch (bytes[0]) {46        inline_tag => .inline_value,47        overflow_tag => .overflow,48        else => error.InvalidRecord,49    };50}5152pub fn inlineValue(bytes: []const u8) Error![]const u8 {53    if (bytes.len == 0 or bytes[0] != inline_tag) return error.InvalidRecord;54    return bytes[1..];55}5657pub fn overflow(bytes: []const u8) Error!Overflow {58    if (bytes.len != overflow_size) return error.InvalidRecord;59    if (bytes[0] != overflow_tag) return error.InvalidRecord;60    const value = Overflow{61        .len = std.mem.readInt(u64, bytes[1..][0..8], .big),62        .first_page = std.mem.readInt(u32, bytes[9..][0..4], .big),63    };64    if (value.len == 0 or value.first_page == 0) return error.InvalidRecord;65    return value;66}6768test "record encodes inline values" {69    var bytes: [16]u8 = undefined;70    const encoded = try encodeInline(&bytes, "value");7172    try std.testing.expectEqual(Kind.inline_value, try kind(encoded));73    try std.testing.expectEqualStrings("value", try inlineValue(encoded));74    try std.testing.expectError(error.InvalidRecord, overflow(encoded));75}7677test "record encodes overflow references" {78    var bytes: [overflow_size]u8 = undefined;79    const encoded = try encodeOverflow(&bytes, .{80        .len = 9000,81        .first_page = 42,82    });83    const decoded = try overflow(encoded);8485    try std.testing.expectEqual(Kind.overflow, try kind(encoded));86    try std.testing.expectEqual(@as(u64, 9000), decoded.len);87    try std.testing.expectEqual(@as(u32, 42), decoded.first_page);88    try std.testing.expectError(error.InvalidRecord, inlineValue(encoded));89}

1pub const record = @import("record.zig");