zip: read in memory (#10960)

vlib/szip/szip.v

@@ -17,6 +17,8 @@ fn C.zip_close(&Zip)
 
 fn C.zip_entry_open(&Zip, &byte) int
 
+fn C.zip_entry_openbyindex(&Zip, int) int
+
 fn C.zip_entry_close(&Zip) int
 
 fn C.zip_entry_name(&Zip) &byte
@@ -35,6 +37,8 @@ fn C.zip_entry_fwrite(&Zip, &char) int
 
 fn C.zip_entry_read(&Zip, &voidptr, &size_t) int
 
+fn C.zip_entry_noallocread(&Zip, voidptr, size_t) int
+
 fn C.zip_entry_fread(&Zip, &char) int
 
 fn C.zip_total_entries(&Zip) int
@@ -108,6 +112,14 @@ pub fn (mut zentry Zip) open_entry(name string) ? {
 	}
 }
 
+// open_entry_by_index opens an entry by index in the archive.
+pub fn (mut z Zip) open_entry_by_index(index int) ? {
+	res := C.zip_entry_openbyindex(z, index)
+	if res == -1 {
+		return error('szip: cannot open archive entry at index $index')
+	}
+}
+
 // close_entry closes a zip entry, flushes buffer and releases resources.
 [inline]
 pub fn (mut zentry Zip) close_entry() {
@@ -192,6 +204,16 @@ pub fn (mut zentry Zip) read_entry() ?voidptr {
 	return buf
 }
 
+// read_entry_buf extracts the current zip entry into user specified buffer
+pub fn (mut zentry Zip) read_entry_buf(buf voidptr, in_bsize int) ?int {
+	bsize := size_t(in_bsize)
+	res := C.zip_entry_noallocread(zentry, buf, bsize)
+	if res == -1 {
+		return error('szip: cannot read properly data from entry')
+	}
+	return res
+}
+
 // extract_entry extracts the current zip entry into output file.
 pub fn (mut zentry Zip) extract_entry(path string) ? {
 	if !os.is_file(path) {

vlib/szip/szip_test.v

@@ -4,8 +4,10 @@ import os
 const (
 	test_out_zip = 'v_test_zip.zip'
 	test_path    = 'zip files'
-	fpath1       = os.join_path(test_path, 'file_1.txt')
-	fpath2       = os.join_path(test_path, 'file_2.txt')
+	fname1       = 'file_1.txt'
+	fpath1       = os.join_path(test_path, fname1)
+	fname2       = 'file_2.txt'
+	fpath2       = os.join_path(test_path, fname2)
 )
 
 fn test_szip_create_temp_files() ? {
@@ -35,3 +37,52 @@ fn test_extract_zipped_files() ? {
 	os.rmdir_all(test_path) ?
 	os.rm(test_out_zip) or {}
 }
+
+fn test_reading_zipping_files() ? {
+	n_files := 2
+	mut file_name_list := []string{}
+	for i in 0 .. n_files {
+		file_name_list << 'file_${i:02}.txt'
+	}
+
+	os.chdir(os.temp_dir())
+	os.rmdir_all(test_path) or {}
+	os.mkdir(test_path) ?
+	for c, f_name in file_name_list {
+		tmp_path := os.join_path(test_path, f_name)
+		os.write_file(tmp_path, 'file ${c:02}') ?
+		assert os.exists(tmp_path)
+	}
+	files := (os.ls(test_path) ?).map(os.join_path(test_path, it))
+
+	szip.zip_files(files, test_out_zip) ?
+	assert os.exists(test_out_zip)
+
+	mut zp := szip.open(test_out_zip, szip.CompressionLevel.no_compression, szip.OpenMode.read_only) ?
+	n_entries := zp.total() ?
+	assert n_entries == n_files
+
+	unsafe {
+		data_len := 'file XX'.len
+		buf_size := 32
+		buf := malloc(data_len * 2)
+
+		for _ in 0 .. n_files {
+			zp.open_entry_by_index(0) ?
+			name := zp.name()
+			assert name in file_name_list
+
+			zp.read_entry_buf(buf, buf_size) ?
+			buf[data_len] = 0
+			tmp_str := tos(buf, data_len)
+
+			assert tmp_str[0..4] == 'file'
+			assert tmp_str[5..7] == name[5..7]
+
+			zp.close_entry()
+		}
+
+		free(buf)
+	}
+	zp.close()
+}