patch 9.1.1016: Not possible to convert string2blob and blob2string

Problem:  Not possible to convert string2blob and blob2string
Solution: add support for the blob2str() and str2blob() functions

closes: #16373

Signed-off-by: Yegappan Lakshmanan <yegappan@yahoo.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

runtime/doc/builtin.txt

@@ -1,4 +1,4 @@
-*builtin.txt*	For Vim version 9.1.  Last change: 2025 Jan 06
+*builtin.txt*	For Vim version 9.1.  Last change: 2025 Jan 14
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -72,6 +72,7 @@ base64_encode({blob})		String	base64 encode the bytes in {blob}
 bindtextdomain({package}, {path})
 				Bool	bind text domain to specified path
 blob2list({blob})		List	convert {blob} into a list of numbers
+blob2str({blob} [, {options}])	String	convert {blob} into a String
 browse({save}, {title}, {initdir}, {default})
 				String	put up a file requester
 browsedir({title}, {initdir})	String	put up a directory requester
@@ -609,6 +610,8 @@ split({expr} [, {pat} [, {keepempty}]])
 sqrt({expr})			Float	square root of {expr}
 srand([{expr}])			List	get seed for |rand()|
 state([{what}])			String	current state of Vim
+str2blob({string} [, {options}])
+				Blob	convert {string} into a Blob
 str2float({expr} [, {quoted}])	Float	convert String to Float
 str2list({expr} [, {utf8}])	List	convert each character of {expr} to
 					ASCII/UTF-8 value
@@ -1289,6 +1292,38 @@ blob2list({blob})					*blob2list()*
 <
 		Return type: list<any> or list<number>
 
+
+blob2str({blob} [, {options}])				*blob2str()*
+		Return a String in the current 'encoding' by converting the
+		bytes in {blob} into characters.
+
+		If {options} is not supplied, the current 'encoding' value is
+		used to decode the bytes in {blob}.
+
+		The argument {options} is a |Dict| and supports the following
+		items:
+		    encoding	Decode the bytes in {blob} using this
+				encoding.  The value is a |String|.  See
+				|encoding-names| for the supported values.
+							*E1515*
+		An error is given and an empty string is returned if
+		an invalid byte sequence is encountered in {blob},
+
+		Returns an empty String if blob is empty.
+
+		See also |str2blob()|
+
+		Examples: >
+			blob2str(0z6162)	returns "ab"
+			blob2str(0zC2ABC2BB)	returns "«»"
+			blob2str(0zABBB, {'encoding': 'latin1'})  returns "«»"
+<
+		Can also be used as a |method|: >
+			GetBlob()->blob2str()
+<
+		Return type: |String|
+
+
 							*browse()*
 browse({save}, {title}, {initdir}, {default})
 		Put up a file requester.  This only works when "has("browse")"
@@ -10556,6 +10591,36 @@ state([{what}])						*state()*
 		Return type: |String|
 
 
+str2blob({string} [, {options}])				*str2blob()*
+		Return a Blob by converting the characters in {string} into
+		bytes.
+
+		If {options} is not supplied, the current 'encoding' value is
+		used to convert the characters in {string} into bytes.
+
+		The argument {options} is a |Dict| and supports the following
+		items:
+		    encoding	Encode the characters in {string} using this
+				encoding.  The value is a |String|.  See
+				|encoding-names| for the supported values.
+
+		An error is given and an empty blob is returned if the
+		character encoding fails.
+
+		Returns an empty Blob if {string} is empty.
+
+		See also |blob2str()|
+
+		Examples: >
+			str2blob("ab")		returns 0z6162
+			str2blob("«»")		returns 0zC2ABC2BB
+			str2blob("«»", {'encoding': 'latin1'})	returns 0zABBB
+<
+		Can also be used as a |method|: >
+			GetStr()->str2blob()
+<
+		Return type: |Blob|
+
 str2float({string} [, {quoted}])				*str2float()*
 		Convert String {string} to a Float.  This mostly works the
 		same as when using a floating point number in an expression,

runtime/doc/tags

@@ -4585,6 +4585,7 @@ E1511	options.txt	/*E1511*
 E1512	options.txt	/*E1512*
 E1513	message.txt	/*E1513*
 E1514	options.txt	/*E1514*
+E1515	builtin.txt	/*E1515*
 E152	helphelp.txt	/*E152*
 E153	helphelp.txt	/*E153*
 E154	helphelp.txt	/*E154*
@@ -6192,6 +6193,7 @@ blob-index	eval.txt	/*blob-index*
 blob-literal	eval.txt	/*blob-literal*
 blob-modification	eval.txt	/*blob-modification*
 blob2list()	builtin.txt	/*blob2list()*
+blob2str()	builtin.txt	/*blob2str()*
 blockwise-examples	visual.txt	/*blockwise-examples*
 blockwise-operators	visual.txt	/*blockwise-operators*
 blockwise-put	change.txt	/*blockwise-put*
@@ -10253,6 +10255,7 @@ status-line	windows.txt	/*status-line*
 statusmsg-variable	eval.txt	/*statusmsg-variable*
 stl-%!	options.txt	/*stl-%!*
 stl-%{	options.txt	/*stl-%{*
+str2blob()	builtin.txt	/*str2blob()*
 str2float()	builtin.txt	/*str2float()*
 str2list()	builtin.txt	/*str2list()*
 str2nr()	builtin.txt	/*str2nr()*

runtime/doc/usr_41.txt

@@ -1,4 +1,4 @@
-*usr_41.txt*	For Vim version 9.1.  Last change: 2025 Jan 02
+*usr_41.txt*	For Vim version 9.1.  Last change: 2025 Jan 14
 
 		     VIM USER MANUAL - by Bram Moolenaar
 
@@ -801,6 +801,8 @@ String manipulation:					*string-functions*
 	trim()			trim characters from a string
 	bindtextdomain()	set message lookup translation base path
 	gettext()		lookup message translation
+	str2blob()		convert a string into a blob
+	blob2str()		convert a blob into a string
 
 List manipulation:					*list-functions*
 	get()			get an item without error for wrong index

runtime/doc/version9.txt

@@ -1,4 +1,4 @@
-*version9.txt*  For Vim version 9.1.  Last change: 2025 Jan 12
+*version9.txt*  For Vim version 9.1.  Last change: 2025 Jan 14
 
 
 		  VIM REFERENCE MANUAL    by Bram Moolenaar
@@ -41638,6 +41638,7 @@ Functions: ~
 
 |base64_decode()|	decode a base64 string into a blob
 |base64_encode()|	encode a blob into a base64 string
+|blob2str()|		convert a blob into a string
 |bindtextdomain()|	set message lookup translation base path
 |diff()|		diff two Lists of strings
 |filecopy()|		copy a file {from} to {to}
@@ -41653,6 +41654,7 @@ Functions: ~
 |matchbufline()|	all the matches of a pattern in a buffer
 |matchstrlist()|	all the matches of a pattern in a List of strings
 |popup_setbuf()|	switch to a different buffer in a popup
+|str2blob()|		convert a string into a blob
 
 
 Autocommands: ~

src/errors.h

@@ -3657,3 +3657,5 @@ EXTERN char e_winfixbuf_cannot_go_to_buffer[]
 	INIT(= N_("E1513: Cannot switch buffer. 'winfixbuf' is enabled"));
 EXTERN char e_invalid_return_type_from_findfunc[]
 	INIT(= N_("E1514: 'findfunc' did not return a List type"));
+EXTERN char e_str_encoding_failed[]
+	INIT(= N_("E1515: Unable to convert %s '%s' encoding"));

src/evalfunc.c

@@ -1151,6 +1151,7 @@ static argcheck_T arg2_string_number[] = {arg_string, arg_number};
 static argcheck_T arg2_string_or_list_dict[] = {arg_string_or_list_any, arg_dict_any};
 static argcheck_T arg2_string_or_list_number[] = {arg_string_or_list_any, arg_number};
 static argcheck_T arg2_string_string_or_number[] = {arg_string, arg_string_or_nr};
+static argcheck_T arg2_blob_dict[] = {arg_blob, arg_dict_any};
 static argcheck_T arg3_any_list_dict[] = {arg_any, arg_list_any, arg_dict_any};
 static argcheck_T arg3_buffer_lnum_lnum[] = {arg_buffer, arg_lnum, arg_lnum};
 static argcheck_T arg3_buffer_number_number[] = {arg_buffer, arg_number, arg_number};
@@ -1844,6 +1845,8 @@ static funcentry_T global_functions[] =
 			ret_bool,	    f_bindtextdomain},
     {"blob2list",	1, 1, FEARG_1,	    arg1_blob,
 			ret_list_number,    f_blob2list},
+    {"blob2str",	1, 2, FEARG_1,	    arg2_blob_dict,
+			ret_string,	    f_blob2str},
     {"browse",		4, 4, 0,	    arg4_browse,
 			ret_string,	    f_browse},
     {"browsedir",	2, 2, 0,	    arg2_string,
@@ -2710,6 +2713,8 @@ static funcentry_T global_functions[] =
 			ret_list_number,    f_srand},
     {"state",		0, 1, FEARG_1,	    arg1_string,
 			ret_string,	    f_state},
+    {"str2blob",	1, 2, FEARG_1,	    arg2_string_dict,
+			ret_blob,	    f_str2blob},
     {"str2float",	1, 2, FEARG_1,	    arg2_string_bool,
 			ret_float,	    f_str2float},
     {"str2list",	1, 2, FEARG_1,	    arg2_string_bool,

src/mbyte.c

@@ -2106,6 +2106,17 @@ utf_byte2len(int b)
     return utf8len_tab[b];
 }
 
+/*
+ * Return length of UTF-8 character, obtained from the first byte.
+ * "b" must be between 0 and 255!
+ * Returns 0 for an invalid first byte value.
+ */
+    int
+utf_byte2len_zero(int b)
+{
+    return utf8len_tab_zero[b];
+}
+
 /*
  * Get the length of UTF-8 byte sequence "p[size]".  Does not include any
  * following composing characters.

src/proto/mbyte.pro

@@ -31,6 +31,7 @@ int utfc_ptr2char_len(char_u *p, int *pcc, int maxlen);
 int utfc_char2bytes(int off, char_u *buf);
 int utf_ptr2len(char_u *p);
 int utf_byte2len(int b);
+int utf_byte2len_zero(int b);
 int utf_ptr2len_len(char_u *p, int size);
 int utfc_ptr2len(char_u *p);
 int utfc_ptr2len_len(char_u *p, int size);

src/proto/strings.pro

@@ -31,6 +31,8 @@ void string_reduce(typval_T *argvars, typval_T *expr, typval_T *rettv);
 void f_byteidx(typval_T *argvars, typval_T *rettv);
 void f_byteidxcomp(typval_T *argvars, typval_T *rettv);
 void f_charidx(typval_T *argvars, typval_T *rettv);
+void f_blob2str(typval_T *argvars, typval_T *rettv);
+void f_str2blob(typval_T *argvars, typval_T *rettv);
 void f_str2list(typval_T *argvars, typval_T *rettv);
 void f_str2nr(typval_T *argvars, typval_T *rettv);
 void f_strgetchar(typval_T *argvars, typval_T *rettv);

src/strings.c

@@ -1213,6 +1213,146 @@ f_charidx(typval_T *argvars, typval_T *rettv)
     rettv->vval.v_number = len > 0 ? len - 1 : 0;
 }
 
+/*
+ * Convert the string "str", from encoding "from" to encoding "to".
+ */
+    static char_u *
+convert_string(char_u *str, char_u *from, char_u *to)
+{
+    vimconv_T	vimconv;
+
+    vimconv.vc_type = CONV_NONE;
+    if (convert_setup(&vimconv, from, to) == FAIL)
+	return NULL;
+    vimconv.vc_fail = TRUE;
+    if (vimconv.vc_type == CONV_NONE)
+	str = vim_strsave(str);
+    else
+	str = string_convert(&vimconv, str, NULL);
+    convert_setup(&vimconv, NULL, NULL);
+
+    return str;
+}
+
+/*
+ * "blob2str()" function
+ * Converts a blob to a string, ensuring valid UTF-8 encoding.
+ */
+    void
+f_blob2str(typval_T *argvars, typval_T *rettv)
+{
+    blob_T  *blob;
+    char_u  *str;
+    char_u  *p;
+    int	    blen;
+
+    if (check_for_blob_arg(argvars, 0) == FAIL
+	    || check_for_opt_dict_arg(argvars, 1) == FAIL)
+	return;
+
+    blob = argvars->vval.v_blob;
+    blen = blob_len(blob);
+
+    rettv->v_type = VAR_STRING;
+
+    str = alloc(blen + 1);
+    if (str == NULL)
+	return;
+
+    for (int i = 0; i < blen; i++)
+	str[i] = (char_u)blob_get(blob, i);
+    str[blen] = NUL;
+
+    p = str;
+    if (argvars[1].v_type != VAR_UNKNOWN)
+    {
+	dict_T *d = argvars[1].vval.v_dict;
+	if (d != NULL)
+	{
+	    char_u *enc = dict_get_string(d, "encoding", FALSE);
+	    if (enc != NULL)
+	    {
+		char_u *from = enc_canonize(enc_skip(enc));
+		p = convert_string(str, from, p_enc);
+		vim_free(str);
+		if (p == NULL)
+		{
+		    semsg(_(e_str_encoding_failed), "from", from);
+		    vim_free(from);
+		    return;
+		}
+		vim_free(from);
+	    }
+	}
+    }
+
+    if (STRCMP(p_enc, "utf-8") == 0 || STRCMP(p_enc, "utf8") == 0)
+    {
+	if (!utf_valid_string(p, NULL))
+	{
+	    semsg(_(e_str_encoding_failed), "from", p_enc);
+	    vim_free(p);
+	    return;
+	}
+    }
+
+    rettv->vval.v_string = p;
+}
+
+/*
+ * "str2blob()" function
+ */
+    void
+f_str2blob(typval_T *argvars, typval_T *rettv)
+{
+    blob_T	*blob;
+    char_u	*p;
+    size_t	len;
+
+    if (check_for_string_arg(argvars, 0) == FAIL
+	    || check_for_opt_dict_arg(argvars, 1) == FAIL)
+	return;
+
+    if (rettv_blob_alloc(rettv) == FAIL)
+	return;
+
+    blob = rettv->vval.v_blob;
+
+    p = tv_get_string_chk(&argvars[0]);
+    if (p == NULL)
+	return;
+
+    int free_str = FALSE;
+    if (argvars[1].v_type != VAR_UNKNOWN)
+    {
+	dict_T *d = argvars[1].vval.v_dict;
+	if (d != NULL)
+	{
+	    char_u *enc = dict_get_string(d, "encoding", FALSE);
+	    if (enc != NULL)
+	    {
+		char_u *to = enc_canonize(enc_skip(enc));
+		p = convert_string(p, p_enc, to);
+		if (p == NULL)
+		{
+		    semsg(_(e_str_encoding_failed), "to", to);
+		    vim_free(to);
+		    return;
+		}
+		vim_free(to);
+		free_str = TRUE;
+	    }
+	}
+    }
+
+    len = STRLEN(p);
+    for (size_t i = 0; i < len; i++)
+	ga_append(&blob->bv_ga, (int)p[i]);
+
+    if (free_str)
+	vim_free(p);
+}
+
 /*
  * "str2list()" function
  */

src/testdir/test_functions.vim

@@ -4257,4 +4257,73 @@ func Test_base64_encoding()
   call v9.CheckLegacyAndVim9Success(lines)
 endfunc
 
+" Tests for the str2blob() function
+func Test_str2blob()
+  let lines =<< trim END
+    call assert_equal(0z, str2blob(""))
+    call assert_fails("call str2blob([])", 'E1174: String required for argument 1')
+    call assert_equal(0z6162, str2blob("ab"))
+    call assert_equal(0zC2ABC2BB, str2blob("«»"))
+    call assert_equal(0zC59DC59F, str2blob("ŝş"))
+    call assert_equal(0zE0AE85E0.AE87, str2blob("அஇ"))
+    call assert_equal(0zF09F81B0.F09F81B3, str2blob("🁰🁳"))
+    call assert_equal(0z616263, str2blob('abc', {}))
+    call assert_equal(0zABBB, str2blob('«»', {'encoding': 'latin1'}))
+    call assert_equal(0zC2ABC2BB, str2blob('«»', {'encoding': 'utf8'}))
+
+    call assert_fails("call str2blob('abc', [])", 'E1206: Dictionary required for argument 2')
+    call assert_fails("call str2blob('abc', {'encoding': []})", 'E730: Using a List as a String')
+    call assert_fails("call str2blob('abc', {'encoding': 'ab12xy'})", 'E1515: Unable to convert to ''ab12xy'' encoding')
+    call assert_fails("call str2blob('ŝş', {'encoding': 'latin1'})", 'E1515: Unable to convert to ''latin1'' encoding')
+    call assert_fails("call str2blob('அஇ', {'encoding': 'latin1'})", 'E1515: Unable to convert to ''latin1'' encoding')
+    call assert_fails("call str2blob('🁰🁳', {'encoding': 'latin1'})", 'E1515: Unable to convert to ''latin1'' encoding')
+  END
+  call v9.CheckLegacyAndVim9Success(lines)
+endfunc
+
+" Tests for the blob2str() function
+func Test_blob2str()
+  let lines =<< trim END
+    call assert_equal("", blob2str(0z))
+    call assert_fails("call blob2str([])", 'E1238: Blob required for argument 1')
+    call assert_equal("ab", blob2str(0z6162))
+    call assert_equal("«»", blob2str(0zC2ABC2BB))
+    call assert_equal("ŝş", blob2str(0zC59DC59F))
+    call assert_equal("அஇ", blob2str(0zE0AE85E0.AE87))
+    call assert_equal("🁰🁳", blob2str(0zF09F81B0.F09F81B3))
+    call assert_equal('«»', blob2str(0zABBB, {'encoding': 'latin1'}))
+    call assert_equal('«»', blob2str(0zC2ABC2BB, {'encoding': 'utf8'}))
+
+    #" Invalid encoding
+    call assert_fails("call blob2str(0z80)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0zC0)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0zE0)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0zF0)", "E1515: Unable to convert from 'utf-8' encoding")
+
+    call assert_fails("call blob2str(0z6180)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0z61C0)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0z61E0)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0z61F0)", "E1515: Unable to convert from 'utf-8' encoding")
+
+    call assert_fails("call blob2str(0zC0C0)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0z61C0C0)", "E1515: Unable to convert from 'utf-8' encoding")
+
+    call assert_fails("call blob2str(0zE0)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0zE080)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0zE080C0)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0z61E080C0)", "E1515: Unable to convert from 'utf-8' encoding")
+
+    call assert_fails("call blob2str(0zF08080C0)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0z61F08080C0)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0zF0)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0zF080)", "E1515: Unable to convert from 'utf-8' encoding")
+    call assert_fails("call blob2str(0zF08080)", "E1515: Unable to convert from 'utf-8' encoding")
+
+    call assert_fails("call blob2str(0z6162, [])", 'E1206: Dictionary required for argument 2')
+    call assert_fails("call blob2str(0z6162, {'encoding': []})", 'E730: Using a List as a String')
+    call assert_fails("call blob2str(0z6162, {'encoding': 'ab12xy'})", 'E1515: Unable to convert from ''ab12xy'' encoding')
+  END
+  call v9.CheckLegacyAndVim9Success(lines)
+endfunc
+
 " vim: shiftwidth=2 sts=2 expandtab

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1016,
 /**/
     1015,
 /**/