tiny.pdf.content

1const std = @import("std");2const alloc_arena = @import("alloc_arena");34const font = @import("font.zig");5const object = @import("object.zig");67const Piece = union(enum) {8    text: object.String,9    space,10};1112pub fn extractTextAppend(allocator: std.mem.Allocator, out: *std.ArrayList(u8), content: []const u8, fonts: font.Set) !void {13    var parser = object.Parser.init(content, 0);14    var pending_strings: std.ArrayList(Piece) = .empty;15    defer pending_strings.deinit(allocator);16    var arena_state = alloc_arena.Arena.init(allocator);17    defer arena_state.deinit();18    const arena = arena_state.allocator();19    var last_name: ?[]const u8 = null;20    var current_font: ?*const font.Font = null;21    for (content) |_| {22        parser.skipWhitespace();23        if (parser.pos >= content.len) break;24        const byte = content[parser.pos];25        if (byte == '/' or byte == '(' or byte == '<' or byte == '[' or std.ascii.isDigit(byte) or byte == '+' or byte == '-' or byte == '.') {26            const value = parser.parseValue(arena) catch {27                parser.pos += 1;28                continue;29            };30            switch (value) {31                .name => |name| last_name = name,32                else => {},33            }34            try collectStrings(allocator, &pending_strings, value);35            continue;36        }37        const start = parser.pos;38        while (parser.pos < content.len and !object.delimiterOrWhitespace(content[parser.pos])) parser.pos += 1;39        if (parser.pos == start) {40            parser.pos += 1;41            continue;42        }43        const operator = content[start..parser.pos];44        if (std.mem.eql(u8, operator, "Tf")) {45            current_font = if (last_name) |name| fonts.get(name) else null;46        }47        try applyOperator(allocator, out, &pending_strings, operator, current_font);48    }49}5051fn collectStrings(allocator: std.mem.Allocator, pending: *std.ArrayList(Piece), value: object.Value) !void {52    switch (value) {53        .string => |string| try pending.append(allocator, .{ .text = string }),54        .array => |items| {55            for (items) |item| {56                switch (item) {57                    .string => |string| try pending.append(allocator, .{ .text = string }),58                    .integer => |kern| if (kern <= -space_kerning_threshold) try pending.append(allocator, .space),59                    .real => |kern| if (kern <= -@as(f64, space_kerning_threshold)) try pending.append(allocator, .space),60                    else => {},61                }62            }63        },64        else => {},65    }66}6768const space_kerning_threshold = 180;6970fn applyOperator(allocator: std.mem.Allocator, out: *std.ArrayList(u8), pending: *std.ArrayList(Piece), operator: []const u8, current_font: ?*const font.Font) !void {71    if (std.mem.eql(u8, operator, "Tj") or std.mem.eql(u8, operator, "'") or std.mem.eql(u8, operator, "\"") or std.mem.eql(u8, operator, "TJ")) {72        if (std.mem.eql(u8, operator, "'") or std.mem.eql(u8, operator, "\"")) {73            try breakLine(allocator, out);74        }75        for (pending.items) |piece| {76            switch (piece) {77                .text => |string| try appendString(allocator, out, string, current_font),78                .space => {79                    if (out.items.len > 0 and out.items[out.items.len - 1] != ' ' and out.items[out.items.len - 1] != '\n') {80                        try out.append(allocator, ' ');81                    }82                },83            }84        }85        pending.clearRetainingCapacity();86        return;87    }88    if (std.mem.eql(u8, operator, "Td") or std.mem.eql(u8, operator, "TD") or std.mem.eql(u8, operator, "T*") or std.mem.eql(u8, operator, "ET")) {89        try breakLine(allocator, out);90        pending.clearRetainingCapacity();91        return;92    }93    pending.clearRetainingCapacity();94}9596fn appendString(allocator: std.mem.Allocator, out: *std.ArrayList(u8), string: object.String, current_font: ?*const font.Font) !void {97    var raw = std.ArrayList(u8).empty;98    defer raw.deinit(allocator);99    switch (string.kind) {100        .literal => try object.decodeLiteralAppend(allocator, &raw, string.raw),101        .hex => try object.decodeHexAppend(allocator, &raw, string.raw),102    }103    try font.appendText(current_font, allocator, out, raw.items);104}105106fn breakLine(allocator: std.mem.Allocator, out: *std.ArrayList(u8)) !void {107    if (out.items.len == 0) return;108    if (out.items[out.items.len - 1] == '\n') return;109    try out.append(allocator, '\n');110}111112test "content extraction reads show operators lines and tj arrays" {113    var out = std.ArrayList(u8).empty;114    defer out.deinit(std.testing.allocator);115    const content =116        "BT /F1 12 Tf 72 700 Td (Hello, ) Tj (world) Tj T* (second line) Tj " ++117        "0 -14 Td [(kerned) -250 (array) 12 (Close)] TJ ET";118    try extractTextAppend(std.testing.allocator, &out, content, .{});119    try std.testing.expectEqualStrings("Hello, world\nsecond line\nkerned arrayClose\n", out.items);120}121122test "content extraction survives unknown operators and hex strings" {123    var out = std.ArrayList(u8).empty;124    defer out.deinit(std.testing.allocator);125    try extractTextAppend(std.testing.allocator, &out, "q 1 0 0 1 10 10 cm BT <48690A> Tj ET Q", .{});126    try std.testing.expectEqualStrings("Hi\n", out.items);127}128129test "content extraction maps codes through the selected font" {130    const cmap = @import("cmap.zig");131    var arena_state = std.heap.ArenaAllocator.init(std.testing.allocator);132    defer arena_state.deinit();133    const map = try cmap.parseAlloc(134        arena_state.allocator(),135        "1 begincodespacerange <00> <FF> endcodespacerange " ++136            "1 beginbfrange <20> <7E> <0020> endbfrange " ++137            "1 beginbfchar <02> <00660069> endbfchar",138    );139    const mapped = font.Font{ .map = map };140    const plain = font.Font{};141    const set = font.Set{ .entries = &.{142        .{ .name = "F1", .font = &mapped },143        .{ .name = "F2", .font = &plain },144    } };145    var out = std.ArrayList(u8).empty;146    defer out.deinit(std.testing.allocator);147    try extractTextAppend(148        std.testing.allocator,149        &out,150        "BT /F1 9 Tf (Arti\\002cial) Tj /F2 9 Tf ( raw\\002) Tj ET",151        set,152    );153    try std.testing.expectEqualStrings("Artificial raw\x02\n", out.items);154}

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