wrong output from small D program - debugging

Question

I have a written a small utility in D to convert the output of find -print0 to printf %b format. Such a utility already exists (nul2pfb from http://www.dwheeler.com/essays/filenames-in-shell.html), but the link is dead and I could not find the program, so I decided to implement it myself in D. I am using the following zsh command for testing:
diff <(find) <(for i in "$(find -print0 | dd | char2code)"; do printf '%b\n' "$i"; done)
The expected output is empty, but I find that some filenames that include a hyphen are handled wrong.
My source code is this:
import std.stdio;
import std.conv;
import std.ascii;
import std.c.stdlib;
void main()
{
foreach (ubyte[] mybuff; chunks(stdin, 4096)) {
encodeline (mybuff);
}
}
#safe void encodeline (ubyte[] mybuff) {
// char[] outstring;
foreach (ubyte i; mybuff) {
char b = to!char(i);
switch (i) {
case 'a': .. case 'z':
case 'A': .. case 'Z':
case '0': .. case '9':
case '/':
case '.':
case '_':
case ':': writeChar(b); break;
default: writeOctal(b); break;
case 0: writeChar ('\n'); break;
case '\\': writeString(`\\`); break;
case '\t': writeString(`\t`); break;
case '\n': writeString(`\n`); break;
case '\r': writeString(`\r`); break;
case '\f': writeString(`\f`); break;
case '\v': writeString(`\v`); break;
case '\a': writeString(`\a`); break;
case '\b': writeString(`\b`); break;
}
}
// writeString (outstring);
}
#trusted void writeString (string a)
{
write (a);
}
#trusted void writeOctal (int a)
{
try
{
writef ("\\%.#o", a); // leading 0 needed for for zsh printf '%b'
}
catch (std.format.FormatException b)
{
write ("Format exception in function writeOctal");
throw b;
}
}
#trusted void writeChar (char a)
{
try
{
write (a);
}
catch (std.format.FormatException b)
{
write ("Format exception in function writeChar");
throw b;
}
}
#trusted void writeNewline ()
{
writeln;
}
Here is a part of the diff output:
Correct filenames:
./.ibam/profile-004-battery
./.ibam/profile-034-charge
./.ibam/profile-054-charge
./.ibam/profile-045-battery
(a bunch of lines skipped)
---
Wrong filenames:
./.ibam/profileh04-battery
./.ibam/profileh34-charge
./.ibam/profileh54-charge
./.ibam/profileh45-battery
It seems like -0 is being replaced by h.
UPDATE: Replacing .# with .4 in the conversion specifier for writef fixed the problem but I still see differences in output of searches through /proc. However, this is also true when I do (as root)
diff <(find / print) <(find / print) > (myhomedirectory)/log.txt
so I have chosen to ignore it.

Answer 1

As it turned out, the problem was that whenever an octal escape sequence was followed by a number between 0 and 7 inclusive, and the original escape sequence was not already 4 octal digits long, the number became part of the octal escape sequence, causing printf %b to produce incorrect output. This was fixed by replacing the # by .4 in the conversion specifier in the D program.
This is the corrected source code, with some unneeded functions deleted:
import std.stdio;
import std.conv;
import std.ascii;
import std.c.stdlib;
void main()
{
foreach (ubyte[] mybuff; chunks(stdin, 4096)) {
encodeline (mybuff);
}
}
#safe void encodeline (ubyte[] mybuff) {
// char[] outstring;
foreach (ubyte i; mybuff) {
char b = to!char(i);
switch (i) {
case 'a': .. case 'z':
case 'A': .. case 'Z':
case '0': .. case '9':
case '/':
case '.':
case '_':
case ':': writeChar(b); break;
default: writeOctal(b); break;
case 0: writeChar ('\n'); break;
case '\\': writeString(`\\`); break;
case '\t': writeString(`\t`); break;
case '\n': writeString(`\n`); break;
case '\r': writeString(`\r`); break;
case '\f': writeString(`\f`); break;
case '\v': writeString(`\v`); break;
case '\a': writeString(`\a`); break;
case '\b': writeString(`\b`); break;
}
}
}
#trusted void writeString (string a)
{
write (a);
}
#trusted void writeOctal (int a)
{
writef ("\\%.4o", a); // leading 0 needed for for zsh printf '%b'
}
#trusted void writeChar (char a)
{
write (a);
}