Guess that any non-UTF-8 attributes are encoded as ISO-8859-1

shapefile.cpp

@@ -4,6 +4,7 @@
 #include "serial.hpp"
 #include "projection.hpp"
 #include "main.hpp"
+#include "text.hpp"
 #include "milo/dtoa_milo.h"
 
 static void check(size_t bits, void *p, void *end) {
@@ -41,6 +42,30 @@ static double toDouble(unsigned char *ba) {
 	return *((double *) ba);
 }
 
+std::string forceutf8(std::string const &s) {
+	if (check_utf8(s).size() == 0) {
+		return s;
+	}
+
+	std::string out;
+	for (size_t i = 0; i < s.size(); i++) {
+		to_utf8(s[i] & 0xFF, out);
+	}
+
+	static bool warned = false;
+	if (!warned) {
+		std::string trimmed = out;
+		while (trimmed.size() > 0 && trimmed[trimmed.size() - 1] == ' ') {
+			trimmed.pop_back();
+		}
+
+		fprintf(stderr, "Warning: string \"%s\" is not UTF-8; assuming ISO-8859-1\n", trimmed.c_str());
+		warned = true;
+	}
+
+	return out;
+}
+
 drawvec decode_geometry(unsigned char *data, size_t len, int *type) {
 	drawvec dv;
 
@@ -235,7 +260,7 @@ void parse_shapefile(struct serialization_state *sst, std::string fname, int lay
 			}
 		}
 
-		columns.push_back(std::string((char *) dbcolumns + i, j - i));
+		columns.push_back(forceutf8(std::string((char *) dbcolumns + i, j - i)));
 		column_widths.push_back(dbcolumns[i + 16]);
 		column_types.push_back(dbcolumns[i + 11]);
 	}
@@ -274,7 +299,7 @@ void parse_shapefile(struct serialization_state *sst, std::string fname, int lay
 
 			size_t dbp = 1;
 			for (size_t i = 0; i < columns.size(); i++) {
-				std::string s = std::string((char *) (db + dbp), column_widths[i]);
+				std::string s = forceutf8(std::string((char *) (db + dbp), column_widths[i]));
 				dbp += column_widths[i];
 
 				while (s.size() > 0 && s[s.size() - 1] == ' ') {

text.cpp

@@ -5,7 +5,7 @@
  * Returns an empty string if `s` is valid utf8;
  * otherwise returns an error message.
  */
-std::string check_utf8(std::string s) {
+std::string check_utf8(std::string const &s) {
 	for (size_t i = 0; i < s.size(); i++) {
 		size_t fail = 0;
 
@@ -122,3 +122,21 @@ std::string truncate16(std::string const &s, size_t runes) {
 
 	return std::string(s, 0, lastgood - start);
 }
+
+void to_utf8(unsigned ch, std::string &s) {
+	if (ch <= 0x7F) {
+		s.push_back(ch);
+	} else if (ch <= 0x7FF) {
+		s.push_back(0xC0 | (ch >> 6));
+		s.push_back(0x80 | (ch & 0x3F));
+	} else if (ch < 0xFFFF) {
+		s.push_back(0xE0 | (ch >> 12));
+		s.push_back(0x80 | ((ch >> 6) & 0x3F));
+		s.push_back(0x80 | (ch & 0x3F));
+	} else {
+		s.push_back(0xF0 | (ch >> 18));
+		s.push_back(0x80 | ((ch >> 12) & 0x3F));
+		s.push_back(0x80 | ((ch >> 6) & 0x3F));
+		s.push_back(0x80 | (ch & 0x3F));
+	}
+}

text.hpp

@@ -3,8 +3,9 @@
 
 #include <string>
 
-std::string check_utf8(std::string text);
+std::string check_utf8(std::string const &text);
 const char *utf8_next(const char *s, long *c);
 std::string truncate16(std::string const &s, size_t runes);
+void to_utf8(unsigned c, std::string &s);
 
 #endif