Reset master to testing content

internal/ocr/tsv.go

@@ -0,0 +1,138 @@
+// Copyright (c) 2026 Storm Dragon
+// Authors: Storm Dragon, Angus Kola
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package ocr
+
+import (
+	"bufio"
+	"errors"
+	"fmt"
+	"image"
+	"io"
+	"math"
+	"strconv"
+	"strings"
+	"unicode"
+	"unicode/utf8"
+)
+
+const tsvHeader = "level\tpage_num\tblock_num\tpar_num\tline_num\tword_num\tleft\ttop\twidth\theight\tconf\ttext"
+
+// ParseTSV assembles text and coordinates from a single Tesseract TSV stream.
+// Malformed output is rejected atomically, with no recognized text in errors.
+// The supplied dimensions must describe the actual recognition image.
+func ParseTSV(input io.Reader, width, height int) (Result, error) {
+	if !valid_dimensions(width, height) {
+		return Result{}, ErrInvalidImage
+	}
+	limited := &io.LimitedReader{R: input, N: maxTSVBytes + 1}
+	scanner := bufio.NewScanner(limited)
+	scanner.Buffer(make([]byte, 4096), 64<<10)
+	if !scanner.Scan() || scanner.Text() != tsvHeader {
+		if errors.Is(scanner.Err(), bufio.ErrTooLong) {
+			return Result{}, ErrLimit
+		}
+		return Result{}, fmt.Errorf("%w: TSV header", ErrInvalidOutput)
+	}
+	result := Result{Width: width, Height: height}
+	var text strings.Builder
+	closedLines := make(map[LineID]bool)
+	offset, rows := 0, 0
+	for scanner.Scan() {
+		rows++
+		if rows > maxRows || limited.N <= 0 {
+			return Result{}, ErrLimit
+		}
+		fields := strings.SplitN(scanner.Text(), "\t", 12)
+		if len(fields) != 12 {
+			return Result{}, invalid_row(rows)
+		}
+		var numbers [10]int
+		for index := range numbers {
+			number, err := strconv.ParseInt(fields[index], 10, 32)
+			if err != nil || number < 0 {
+				return Result{}, invalid_row(rows)
+			}
+			numbers[index] = int(number)
+		}
+		level := numbers[0]
+		if level < 1 || level > 5 || numbers[1] < 1 {
+			return Result{}, invalid_row(rows)
+		}
+		for index := 2; index <= 5; index++ {
+			if (index <= level && numbers[index] < 1) || (index > level && numbers[index] != 0) {
+				return Result{}, invalid_row(rows)
+			}
+		}
+		confidence, err := strconv.ParseFloat(fields[10], 64)
+		if err != nil || math.IsNaN(confidence) || math.IsInf(confidence, 0) || confidence < -1 || confidence > 100 {
+			return Result{}, invalid_row(rows)
+		}
+		// Subtraction avoids overflowing 32-bit additions on ARM builds.
+		left, top, boxWidth, boxHeight := numbers[6], numbers[7], numbers[8], numbers[9]
+		if left > width || top > height || boxWidth > width-left || boxHeight > height-top {
+			return Result{}, invalid_row(rows)
+		}
+		wordText := fields[11]
+		if !utf8.ValidString(wordText) || strings.ContainsFunc(wordText, unicode.IsControl) {
+			return Result{}, invalid_row(rows)
+		}
+		if level != 5 {
+			if wordText != "" || confidence != -1 {
+				return Result{}, invalid_row(rows)
+			}
+			continue
+		}
+		if strings.TrimSpace(wordText) == "" {
+			continue
+		}
+		bounds := image.Rect(left, top, left+boxWidth, top+boxHeight)
+		if !valid_word_bounds(bounds, width, height) || strings.TrimSpace(wordText) != wordText {
+			return Result{}, invalid_row(rows)
+		}
+		separatorBytes := 0
+		if len(result.Words) != 0 {
+			separatorBytes = 1
+		}
+		if len(result.Words) >= maxWords || text.Len()+len(wordText)+separatorBytes > MaxTextBytes {
+			return Result{}, ErrLimit
+		}
+		id := LineID{numbers[1], numbers[2], numbers[3], numbers[4]}
+		if len(result.Lines) == 0 || result.Lines[len(result.Lines)-1].ID != id {
+			if closedLines[id] {
+				return Result{}, invalid_row(rows)
+			}
+			if len(result.Lines) != 0 {
+				closedLines[result.Lines[len(result.Lines)-1].ID] = true
+				text.WriteByte('\n')
+				offset++
+			}
+			result.Lines = append(result.Lines, Line{ID: id, Span: Span{Start: offset}, WordStart: len(result.Words)})
+		} else {
+			text.WriteByte(' ')
+			offset++
+		}
+		start := offset
+		text.WriteString(wordText)
+		offset += rune_length(wordText)
+		result.Words = append(result.Words, Word{wordText, confidence, bounds, Span{start, offset}})
+		line := &result.Lines[len(result.Lines)-1]
+		line.End, line.WordEnd = offset, len(result.Words)
+	}
+	if limited.N <= 0 {
+		return Result{}, ErrLimit
+	}
+	if scanner.Err() != nil {
+		if errors.Is(scanner.Err(), bufio.ErrTooLong) {
+			return Result{}, ErrLimit
+		}
+		return Result{}, fmt.Errorf("%w: reading TSV", ErrInvalidOutput)
+	}
+	result.Text = text.String()
+	return result, nil
+}
+
+func invalid_row(row int) error {
+	return fmt.Errorf("%w: TSV row %d", ErrInvalidOutput, row)
+}