Mostly finished data reader

2025-05-20 09:15:00 -05:00
parent 128ed9f001
commit 41a6b0d6f3
6 changed files with 159 additions and 26 deletions
@@ -0,0 +1,62 @@
+const std = @import("std");
+
+const Reader = @import("reader.zig").Reader;
+const DecompressType = @import("decompress.zig").DecompressType;
+const FileHolder = @import("readers/file_holder.zig").FileHolder;
+const FileOffsetReader = @import("readers/file_holder.zig").FileOffsetReader;
+const MetadataReader = @import("readers/metadata.zig").MetadataReader;
+
+const TableError = error{InvalidIndex};
+
+pub fn Table(
+    comptime T: type,
+) type {
+    return struct {
+        alloc: std.mem.Allocator,
+        decomp: DecompressType,
+        holder: *FileHolder,
+        table: []T = &[0]T{},
+        offset: u64,
+        item_count: u32,
+
+        pub fn init(read: *Reader, offset: u64, item_count: u32) Self {
+            return .{
+                .alloc = read.alloc,
+                .decomp = read.super.decomp,
+                .holder = &read.holder,
+                .offset = offset,
+                .item_count = item_count,
+            };
+        }
+        pub fn deinit(self: *Self, alloc: std.mem.Allocator) void {
+            alloc.free(self.table);
+        }
+
+        pub fn getValue(self: *Self, i: u64) !T {
+            if (i >= self.item_count) return TableError.InvalidIndex;
+            if (self.table.len - 1 > i) return self.table[i];
+            var meta_rdr: MetadataReader = undefined;
+            var offset_rdr: FileOffsetReader = undefined;
+            var meta_offset: u64 = 0;
+            var to_read: u32 = 0;
+            while (self.table.len < i) {
+                _ = try self.holder.file.preadAll(std.mem.sliceAsBytes(&meta_offset), self.offset);
+                self.offset += 8;
+                offset_rdr = self.holder.readerAt(meta_offset);
+                meta_rdr = .init(self.alloc, self.decomp, offset_rdr.any());
+                defer meta_rdr.deinit();
+                to_read = @min(self.item_count - self.table.len, comptime blk: {
+                    break :blk 8192 / @sizeOf(T);
+                });
+                if (!self.alloc.resize(self.table, self.table.len + to_read)) {
+                    const alloc_size = self.table.len + to_read;
+                    self.alloc.free(self.table);
+                    self.table = try self.alloc.alloc(T, alloc_size);
+                }
+                _ = try meta_rdr.any().readAll(std.mem.asBytes(self.table[self.table.len - to_read ..]));
+            }
+            return self.table[i];
+        }
+        const Self: type = @This();
+    };
+}