Merge pull request #255 from kellemNegasi/udd-35-concurrent-extractio…

…n-example

[UDD-35] Concurrent Document Extraction Eexample

concurrent-processing/README.md

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+# concurrent processing
+
+UniPDF supports document level concurrent processing. This means processing each document separately in its own go routine.   
+The concurrency is supported on document level for now. Page level concurrency in UniPDF is not safe yet.
+
+## Examples
+- [concurrent_extraction.go](concurrent_extraction.go) Extracts text from multiple documents provided via the command line arguments concurrently and saves the result to a text file.

concurrent-processing/concurrent_extraction.go

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+/*
+ * This example demonstrates how to extract content form multiple documents concurrently
+ * with each document extraction running in its own go routine.
+ * N.B. currently concurrency is supported on a document level which means we can only extract one document per go routine.
+ *
+ * Run as: go run concurrent_extraction.go <input1.pdf> <input2.pdf> <input3.pdf>... <output_dir>
+ */
+
+package main
+
+import (
+	"fmt"
+	"io/fs"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/unidoc/unipdf/v3/common/license"
+	"github.com/unidoc/unipdf/v3/extractor"
+	"github.com/unidoc/unipdf/v3/model"
+)
+
+func init() {
+	// Make sure to load your metered License API key prior to using the library.
+	// If you need a key, you can sign up and create a free one at https://cloud.unidoc.io
+	err := license.SetMeteredKey(os.Getenv(`UNIDOC_LICENSE_API_KEY`))
+	if err != nil {
+		panic(err)
+	}
+}
+
+func main() {
+	if len(os.Args) < 3 {
+		fmt.Printf("Usage: go run concurrent_extraction.go input1.pdf input2.pdf input3.pdf... output_dir\n")
+		os.Exit(1)
+	}
+	inputDocuments := []string{}
+	args := os.Args
+	var outputDir string
+	for i := 1; i < len(args); i++ {
+		if i == len(args)-1 {
+			outputDir = args[i]
+		} else {
+			inputDocuments = append(inputDocuments, args[i])
+		}
+	}
+
+	start := time.Now()
+	runConcurrent(inputDocuments, outputDir)
+	duration := time.Since(start)
+	fmt.Println("time taken for concurrent extraction", duration)
+}
+
+// runConcurrent takes the list of input documents and destination output directory and runs the extraction concurrently.
+func runConcurrent(documents []string, outputDir string) {
+	res := make(chan map[string]string, len(documents))
+
+	err := concurrentExtraction(documents, res)
+	if err != nil {
+		fmt.Printf("Error. extraction failed %v.\n", err)
+	}
+	outputPath := outputDir
+	if _, err := os.Stat(outputPath); err != nil {
+		if os.IsNotExist(err) {
+			err := os.Mkdir(outputPath, fs.ModePerm)
+			if err != nil {
+				fmt.Printf("Error. failed to create directory %s\n", outputPath)
+			}
+		}
+	}
+
+	for i := 0; i < len(documents); i++ {
+		result := <-res
+		for path, content := range result {
+			basename := filepath.Base(path)
+			fileName := strings.TrimSuffix(basename, filepath.Ext(basename)) + ".txt"
+			filePath := filepath.Join(outputPath, fileName)
+			file, err := os.Create(filePath)
+			if err != nil {
+				fmt.Printf("Error. failed to create file. %v\n", err)
+			}
+			_, err = file.WriteString(content)
+			if err != nil {
+				fmt.Printf("Error. failed to write content. %v\n", err)
+			}
+		}
+	}
+}
+
+// concurrentExtraction launches a go routine for each document in `documents` and writes the result of extraction to
+// the channel `res`.
+func concurrentExtraction(documents []string, res chan map[string]string) error {
+	for _, docPath := range documents {
+		filePath := docPath
+		go func(path string, res chan map[string]string) {
+			result, err := extractSingleDoc(path)
+			if err != nil {
+				fmt.Printf("Error. Failed to extract file %v. %v\n", filePath, err)
+			}
+			temp := map[string]string{
+				filePath: result,
+			}
+			res <- temp
+		}(filePath, res)
+	}
+
+	return nil
+}
+
+// extractSingleDoc takes a single file specified by the `filePath` and returns the extracted text.
+func extractSingleDoc(filePath string) (string, error) {
+	pdfReader, _, err := model.NewPdfReaderFromFile(filePath, nil)
+	if err != nil {
+		return "", fmt.Errorf("failed to create pdf reader: %w", err)
+	}
+	pages, err := pdfReader.GetNumPages()
+	if err != nil {
+		return "", err
+	}
+	var result string
+	for i := 0; i < pages; i++ {
+		pageNum := i + 1
+		page, err := pdfReader.GetPage(pageNum)
+		if err != nil {
+			return "", fmt.Errorf("failed to get page %d: %w", pageNum, err)
+		}
+
+		ex, err := extractor.New(page)
+		if err != nil {
+			return "", fmt.Errorf("failed to create extractor: %w", err)
+		}
+
+		text, err := ex.ExtractText()
+		if err != nil {
+			return "", fmt.Errorf("failed to extract text: %w", err)
+		}
+		result += text
+	}
+
+	return result, nil
+}