start C compiler

05/preprocess.b

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+; returns a string of null character-separated preprocessing tokens
+; this corresponds to translation phases 1-3 in the C89 standard
+function split_into_preprocessing_tokens
+	argument filename
+	local fd
+	local file_contents
+	local pptokens
+	local p
+	local c
+	local in
+	local out
+	local n
+	
+	fd = open_r(filename)
+	file_contents = malloc(2000000)
+	pptokens = malloc(2000000)
+	p = file_contents
+	:pptokens_read_loop
+		n = syscall(0, fd, p, 4096)
+		if n == 0 goto pptokens_read_loop_end
+		p += n
+	:pptokens_read_loop_end
+	
+	; okay we read the file. first, delete every backslash-newline sequence (phase 2)
+	local newlines ; we add more newlines to keep line numbers right
+	newlines = 1
+	in = file_contents
+	out = file_contents
+	:backslashnewline_loop
+		c = *1in
+		if c == 0 goto backslashnewline_loop_end
+		if c == 10 goto proper_newline_loop
+		if c != '\ goto not_backslashnewline
+			p = in + 1
+			c = *1p
+			if c != 10 goto not_backslashnewline
+				in += 2 ; skip backlash and newline
+				newlines += 1 ; add one additional newline the next time around to compensate
+				goto backslashnewline_loop
+		:not_backslashnewline
+			*1out = *1in
+			out += 1
+			in += 1
+			goto backslashnewline_loop
+		:proper_newline_loop
+			if newlines == 0 goto proper_newline_loop_end
+			; output a newline
+			*1out = 10
+			out += 1
+			newlines -= 1
+			goto proper_newline_loop
+		:proper_newline_loop_end
+			newlines = 1
+			in += 1
+			goto backslashnewline_loop
+	:backslashnewline_loop_end
+	*1out = 0
+	
+	in = file_contents
+	
+	fputs(1, file_contents)
+	
+	free(file_contents)
+	close(fd)
+	return
+	
+	:unterminated_comment
+		fputs(2, .str_unterminated_comment)
+		fputs(2, filename)
+		fputc(2, 10)
+		exit(1)
+	:str_unterminated_comment
+		string Unterminated comment in file
+		byte 32
+		byte 0