extract debug_log into its own static library; expose log_view iterator instead of raw ring_buffer

debug_log/CMakeLists.txt

@@ -0,0 +1,7 @@
+add_library(debug_log STATIC debug_log.cpp)
+
+target_include_directories(debug_log PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
+
+target_compile_options(debug_log PRIVATE -Wall -Wextra -Wno-unused-parameter)
+
+target_link_libraries(debug_log PUBLIC pico_stdlib)

debug_log/debug_log.cpp

@@ -0,0 +1,28 @@
+#include "debug_log.h"
+#include <cstdarg>
+#include <cstdio>
+#include "ring_buffer.h"
+
+namespace {
+
+constexpr uint16_t LOG_CAP = 32;
+ring_buffer<log_entry, LOG_CAP> buf;
+
+} // namespace
+
+void dlog(std::string_view msg) {
+    buf.push_overwrite(log_entry{static_cast<uint32_t>(time_us_32()), std::string(msg)});
+}
+
+void dlogf(const char* fmt, ...) {
+    char b[128];
+    va_list args;
+    va_start(args, fmt);
+    vsnprintf(b, sizeof(b), fmt, args);
+    va_end(args);
+    dlog(b);
+}
+
+log_view log_entries() {
+    return log_view{buf.data.data(), buf.head, LOG_CAP, buf.used()};
+}

debug_log/debug_log.h

@@ -0,0 +1,52 @@
+#pragma once
+#include <cstdint>
+#include <string>
+#include <string_view>
+#include "pico/time.h"
+
+struct log_entry {
+    uint32_t timestamp_us;
+    std::string message;
+};
+
+class log_iterator {
+    const log_entry* data;
+    uint16_t base;
+    uint16_t cap;
+    uint16_t pos;
+public:
+    log_iterator(const log_entry* d, uint16_t b, uint16_t c, uint16_t p)
+        : data(d), base(b), cap(c), pos(p) {}
+    const log_entry& operator*() const { return data[(base + pos) % cap]; }
+    log_iterator& operator++() { ++pos; return *this; }
+    bool operator!=(const log_iterator& o) const { return pos != o.pos; }
+};
+
+class log_view {
+    const log_entry* data;
+    uint16_t base;
+    uint16_t cap;
+    uint16_t count;
+public:
+    log_view(const log_entry* d, uint16_t b, uint16_t c, uint16_t n)
+        : data(d), base(b), cap(c), count(n) {}
+    log_iterator begin() const { return {data, base, cap, 0}; }
+    log_iterator end() const { return {data, base, cap, count}; }
+};
+
+log_view log_entries();
+
+void dlog(std::string_view msg);
+
+__attribute__((format(printf, 1, 2)))
+void dlogf(const char* fmt, ...);
+
+template <typename F>
+inline void dlog_if_slow(std::string_view label, uint32_t threshold_us, F&& fn) {
+    uint32_t t0 = time_us_32();
+    fn();
+    uint32_t elapsed = time_us_32() - t0;
+    if (elapsed > threshold_us) {
+        dlogf("%.*s %luus", static_cast<int>(label.size()), label.data(), static_cast<unsigned long>(elapsed));
+    }
+}

debug_log/ring_buffer.h

@@ -0,0 +1,67 @@
+#pragma once
+#include <array>
+#include <cstdint>
+#include <span>
+
+template <typename T, uint16_t N>
+struct ring_buffer {
+    std::array<T, N> data = {};
+    uint16_t head = 0;
+    uint16_t tail = 0;
+
+    uint16_t used() const { return tail - head; }
+    uint16_t free() const { return N - used(); }
+    bool empty() const { return head == tail; }
+
+    bool push(std::span<const T> src) {
+        if (src.size() > free()) return false;
+        for (auto& v : src)
+            data[(tail++) % N] = v;
+        return true;
+    }
+
+    bool push(const T& v) {
+        if (free() == 0) return false;
+        data[(tail++) % N] = v;
+        return true;
+    }
+
+    void push_overwrite(const T& v) {
+        if (free() == 0) head++;
+        data[(tail++) % N] = v;
+    }
+
+    uint16_t peek(std::span<T> dst) const {
+        uint16_t len = dst.size() < used() ? dst.size() : used();
+        for (uint16_t i = 0; i < len; i++)
+            dst[i] = data[(head + i) % N];
+        return len;
+    }
+
+    void consume(uint16_t len) {
+        head += len;
+        if (head >= N) {
+            head -= N;
+            tail -= N;
+        }
+    }
+
+    std::span<const T> read_contiguous() const {
+        uint16_t offset = head % N;
+        uint16_t contig = N - offset;
+        uint16_t pending = used();
+        uint16_t len = pending < contig ? pending : contig;
+        return {data.data() + offset, len};
+    }
+
+    struct iterator {
+        const ring_buffer* rb;
+        uint16_t index;
+        const T& operator*() const { return rb->data[(rb->head + index) % N]; }
+        iterator& operator++() { index++; return *this; }
+        bool operator!=(const iterator& o) const { return index != o.index; }
+    };
+
+    iterator begin() const { return {this, 0}; }
+    iterator end() const { return {this, used()}; }
+};