lg2: initial implementation of C++20 structured logging
Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: If37857cc3748df1ea6f767ce535b02c63cde8370
diff --git a/lib/lg2_logger.cpp b/lib/lg2_logger.cpp
new file mode 100644
index 0000000..96e244b
--- /dev/null
+++ b/lib/lg2_logger.cpp
@@ -0,0 +1,232 @@
+#define SD_JOURNAL_SUPPRESS_LOCATION
+
+#include <systemd/sd-journal.h>
+#include <unistd.h>
+
+#include <algorithm>
+#include <bitset>
+#include <cstdarg>
+#include <cstdio>
+#include <iostream>
+#include <phosphor-logging/lg2.hpp>
+#include <vector>
+
+namespace lg2::details
+{
+/** Convert unsigned to string using format flags. */
+static std::string value_to_string(uint64_t f, uint64_t v)
+{
+ switch (f & (hex | bin | dec).value)
+ {
+ // For binary, use bitset<>::to_string.
+ // Treat values without a field-length format flag as 64 bit.
+ case bin.value:
+ {
+ switch (f & (field8 | field16 | field32 | field64).value)
+ {
+ case field8.value:
+ {
+ return "0b" + std::bitset<8>(v).to_string();
+ }
+ case field16.value:
+ {
+ return "0b" + std::bitset<16>(v).to_string();
+ }
+ case field32.value:
+ {
+ return "0b" + std::bitset<32>(v).to_string();
+ }
+ case field64.value:
+ default:
+ {
+ return "0b" + std::bitset<64>(v).to_string();
+ }
+ }
+ }
+
+ // For hex, use the appropriate sprintf.
+ case hex.value:
+ {
+ char value[19];
+ const char* format = nullptr;
+
+ switch (f & (field8 | field16 | field32 | field64).value)
+ {
+ case field8.value:
+ {
+ format = "0x%02" PRIx64;
+ break;
+ }
+
+ case field16.value:
+ {
+ format = "0x%04" PRIx64;
+ break;
+ }
+
+ case field32.value:
+ {
+ format = "0x%08" PRIx64;
+ break;
+ }
+
+ case field64.value:
+ {
+ format = "0x%016" PRIx64;
+ break;
+ }
+
+ default:
+ {
+ format = "0x%" PRIx64;
+ break;
+ }
+ }
+
+ snprintf(value, sizeof(value), format, v);
+ return value;
+ }
+
+ // For dec, use the simple to_string.
+ case dec.value:
+ default:
+ {
+ return std::to_string(v);
+ }
+ }
+}
+
+/** Convert signed to string using format flags. */
+static std::string value_to_string(uint64_t f, int64_t v)
+{
+ // If hex or bin was requested just use the unsigned formatting
+ // rules. (What should a negative binary number look like otherwise?)
+ if (f & (hex | bin).value)
+ {
+ return value_to_string(f, static_cast<uint64_t>(v));
+ }
+ return std::to_string(v);
+}
+
+/** Convert float to string using format flags. */
+static std::string value_to_string(uint64_t, double v)
+{
+ // No format flags supported for floats.
+ return std::to_string(v);
+}
+
+// Positions of various strings in an iovec.
+static constexpr size_t pos_msg = 0;
+static constexpr size_t pos_fmtmsg = 1;
+static constexpr size_t pos_prio = 2;
+static constexpr size_t pos_file = 3;
+static constexpr size_t pos_line = 4;
+static constexpr size_t pos_func = 5;
+static constexpr size_t static_locs = pos_func + 1;
+
+/** No-op output of a message. */
+static void noop_extra_output(level, const std::source_location&,
+ const std::string&)
+{
+}
+
+/** std::cerr output of a message. */
+static void cerr_extra_output(level l, const std::source_location& s,
+ const std::string& m)
+{
+ std::cerr << s.file_name() << ":" << s.line() << ":" << s.function_name()
+ << "|<" << static_cast<uint64_t>(l) << "> " << m << std::endl;
+}
+
+// Use the cerr output method if we are on a TTY.
+static auto extra_output_method =
+ isatty(fileno(stderr)) ? cerr_extra_output : noop_extra_output;
+
+// Do_log implementation.
+void do_log(level l, const std::source_location& s, const std::string_view& m,
+ size_t count, ...)
+{
+ using namespace std::string_literals;
+
+ const size_t entries = count + static_locs;
+ std::vector<std::string> strings{entries};
+
+ std::string message{m};
+
+ // Assign all the static fields.
+ strings[pos_fmtmsg] = "LOG2_FMTMSG="s + m.data();
+ strings[pos_prio] = "PRIORITY="s + std::to_string(static_cast<uint64_t>(l));
+ strings[pos_file] = "CODE_FILE="s + s.file_name();
+ strings[pos_line] = "CODE_LINE="s + std::to_string(s.line());
+ strings[pos_func] = "CODE_FUNC="s + s.function_name();
+
+ // Handle all the va_list args.
+ std::va_list args;
+ va_start(args, count);
+ for (size_t i = static_locs; i < entries; ++i)
+ {
+ // Get the header out.
+ std::string h = va_arg(args, const char*);
+
+ // Get the format flag.
+ auto f = va_arg(args, uint64_t);
+
+ // Handle the value depending on which type format flag it has.
+ std::string value = {};
+ switch (f & (signed_val | unsigned_val | str | floating).value)
+ {
+ case signed_val.value:
+ {
+ auto v = va_arg(args, int64_t);
+ value = value_to_string(f, v);
+ break;
+ }
+
+ case unsigned_val.value:
+ {
+ auto v = va_arg(args, uint64_t);
+ value = value_to_string(f, v);
+ break;
+ }
+
+ case str.value:
+ {
+ value = va_arg(args, const char*);
+ break;
+ }
+
+ case floating.value:
+ {
+ auto v = va_arg(args, double);
+ value = value_to_string(f, v);
+ break;
+ }
+ }
+
+ // Create the field for this value.
+ strings[i] = h + '=' + value;
+
+ // Check for {HEADER} in the message and replace with value.
+ auto h_brace = '{' + h + '}';
+ if (auto start = message.find(h_brace); start != std::string::npos)
+ {
+ message.replace(start, h_brace.size(), value);
+ }
+ }
+ va_end(args);
+
+ // Add the final message into the strings array.
+ strings[pos_msg] = "MESSAGE="s + message.data();
+
+ // Trasform strings -> iovec.
+ std::vector<iovec> iov{};
+ std::ranges::transform(strings, std::back_inserter(iov), [](auto& s) {
+ return iovec{s.data(), s.length()};
+ });
+
+ // Output the iovec.
+ sd_journal_sendv(iov.data(), entries);
+ extra_output_method(l, s, message);
+}
+
+} // namespace lg2::details