Consolidate hex encoding functions into their own file

Consolidate multiple functions doing basically the same hex encoding
and add some tests.

src/CMakeLists.txt

@@ -32,6 +32,7 @@ target_sources(osm2pgsql_lib PRIVATE
     geom-functions.cpp
     geom-pole-of-inaccessibility.cpp
     geom.cpp
+    hex.cpp
     idlist.cpp
     input.cpp
     locator.cpp

src/db-copy-mgr.hpp

@@ -15,7 +15,7 @@
 #include <string>
 
 #include "db-copy.hpp"
-#include "util.hpp"
+#include "hex.hpp"
 
 /**
  * Management class that fills and manages copy buffers.
@@ -237,13 +237,7 @@ public:
      */
     void add_hex_geom(std::string const &wkb)
     {
-        char const *const lookup_hex = "0123456789ABCDEF";
-
-        for (auto c : wkb) {
-            unsigned int const num = static_cast<unsigned char>(c);
-            m_current.buffer += lookup_hex[(num >> 4U) & 0xfU];
-            m_current.buffer += lookup_hex[num & 0xfU];
-        }
+        util::encode_hex(wkb, &m_current.buffer);
         m_current.buffer += '\t';
     }
 

src/gen/canvas.cpp

@@ -9,6 +9,7 @@
 
 #include "canvas.hpp"
 
+#include "hex.hpp"
 #include "raster.hpp"
 #include "tile.hpp"
 
@@ -139,19 +140,3 @@ void canvas_t::merge(canvas_t const &other)
 {
     cv::bitwise_or(m_rast, other.m_rast, m_rast);
 }
-
-std::string to_hex(std::string const &in)
-{
-    std::string result;
-    result.reserve(in.size() * 2);
-
-    char const *const lookup_hex = "0123456789ABCDEF";
-
-    for (const auto c : in) {
-        unsigned int const num = static_cast<unsigned char>(c);
-        result += lookup_hex[(num >> 4U) & 0xfU];
-        result += lookup_hex[num & 0xfU];
-    }
-
-    return result;
-}

src/gen/canvas.hpp

@@ -77,6 +77,4 @@ private:
     image_type m_rast;
 }; // class canvas_t
 
-std::string to_hex(std::string const &in);
-
 #endif // OSM2PGSQL_CANVAS_HPP

src/gen/gen-tile-builtup.cpp

@@ -11,6 +11,7 @@
 
 #include "canvas.hpp"
 #include "geom-functions.hpp"
+#include "hex.hpp"
 #include "logging.hpp"
 #include "params.hpp"
 #include "pgsql.hpp"
@@ -33,7 +34,7 @@ void save_image_to_table(pg_conn_t *connection, canvas_t const &canvas,
                          std::string const &table, char const *variant,
                          std::string const &table_prefix)
 {
-    auto const wkb = to_hex(canvas.to_wkb(tile, margin));
+    auto const wkb = util::encode_hex(canvas.to_wkb(tile, margin));
 
     connection->exec("INSERT INTO \"{}_{}_{}\" (zoom, x, y, rast)"
                      " VALUES ({}, {}, {}, '{}')",
@@ -251,7 +252,7 @@ void gen_tile_builtup_t::process(tile_t const &tile)
     log_gen("Write geometries to destination table...");
     timer(m_timer_write).start();
     for (auto const &geom : geometries) {
-        auto const wkb = to_hex(geom_to_ewkb(geom));
+        auto const wkb = util::encode_hex(geom_to_ewkb(geom));
         if (m_has_area_column) {
             connection().exec_prepared("insert_geoms", wkb, tile.x(), tile.y(),
                                        geom::area(geom));

src/gen/gen-tile-raster.cpp

@@ -10,6 +10,7 @@
 #include "gen-tile-raster.hpp"
 
 #include "canvas.hpp"
+#include "hex.hpp"
 #include "logging.hpp"
 #include "params.hpp"
 #include "pgsql.hpp"
@@ -63,7 +64,7 @@ void save_image_to_table(pg_conn_t *connection, canvas_t const &canvas,
                          std::string const &param, char const *variant,
                          std::string const &table_prefix)
 {
-    auto const wkb = to_hex(canvas.to_wkb(tile, margin));
+    auto const wkb = util::encode_hex(canvas.to_wkb(tile, margin));
 
     connection->exec("INSERT INTO \"{}_{}\" (type, zoom, x, y, rast)"
                      " VALUES ('{}', {}, {}, {}, '{}')",

src/hex.cpp

@@ -0,0 +1,37 @@
+/**
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This file is part of osm2pgsql (https://osm2pgsql.org/).
+ *
+ * Copyright (C) 2006-2025 by the osm2pgsql developer community.
+ * For a full list of authors see the git log.
+ */
+
+#include "hex.hpp"
+
+#include <cassert>
+
+namespace util {
+
+void encode_hex(std::string const &in, std::string *out)
+{
+    assert(out);
+
+    constexpr char const *const LOOKUP_HEX = "0123456789ABCDEF";
+
+    for (auto const c : in) {
+        unsigned int const num = static_cast<unsigned char>(c);
+        (*out) += LOOKUP_HEX[(num >> 4U) & 0xfU];
+        (*out) += LOOKUP_HEX[num & 0xfU];
+    }
+}
+
+std::string encode_hex(std::string const &in)
+{
+    std::string result;
+    result.reserve(in.size() * 2);
+    encode_hex(in, &result);
+    return result;
+}
+
+} // namespace util

src/hex.hpp

@@ -0,0 +1,35 @@
+#ifndef OSM2PGSQL_HEX_HPP
+#define OSM2PGSQL_HEX_HPP
+
+/**
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This file is part of osm2pgsql (https://osm2pgsql.org/).
+ *
+ * Copyright (C) 2006-2025 by the osm2pgsql developer community.
+ * For a full list of authors see the git log.
+ */
+
+#include <string>
+
+namespace util {
+
+/**
+ * Convert content of input string to hex and append to output.
+ *
+ * \param in The input data.
+ * \param out Pointer to output string.
+ */
+void encode_hex(std::string const &in, std::string *out);
+
+/**
+ * Convert content of input string to hex and return it.
+ *
+ * \param in The input data.
+ * \returns Hex encoded string.
+ */
+std::string encode_hex(std::string const &in);
+
+} // namespace util
+
+#endif // OSM2PGSQL_HEX_HPP

tests/CMakeLists.txt

@@ -57,6 +57,7 @@ set_test(test-geom-points LABELS NoDB)
 set_test(test-geom-pole-of-inaccessibility LABELS NoDB)
 set_test(test-geom-polygons LABELS NoDB)
 set_test(test-geom-transform LABELS NoDB)
+set_test(test-hex LABELS NoDB)
 set_test(test-json-writer LABELS NoDB)
 set_test(test-locator LABELS NoDB)
 set_test(test-lua-utils LABELS NoDB)

tests/test-hex.cpp

@@ -0,0 +1,37 @@
+/**
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This file is part of osm2pgsql (https://osm2pgsql.org/).
+ *
+ * Copyright (C) 2006-2025 by the osm2pgsql developer community.
+ * For a full list of authors see the git log.
+ */
+
+#include <catch.hpp>
+
+#include "hex.hpp"
+
+#include <string>
+
+TEST_CASE("hex encode a string", "[NoDB]")
+{
+    std::string result;
+    util::encode_hex("ab~", &result);
+    REQUIRE(result.size() == 6);
+    REQUIRE(result == "61627E");
+}
+
+TEST_CASE("hex encode a string adding to existing string", "[NoDB]")
+{
+    std::string result{"0x"};
+    util::encode_hex("\xca\xfe", &result);
+    REQUIRE(result.size() == 6);
+    REQUIRE(result == "0xCAFE");
+}
+
+TEST_CASE("hex encoding an empty string doesn't change output string", "[NoDB]")
+{
+    std::string result{"foo"};
+    util::encode_hex("", &result);
+    REQUIRE(result == "foo");
+}