Stage 22

clks/kernel/log.c

@@ -4,6 +4,11 @@
 #include <clks/types.h>
 
 #define CLKS_LOG_LINE_MAX 256
+#define CLKS_LOG_JOURNAL_CAP 256
+
+static char clks_log_journal[CLKS_LOG_JOURNAL_CAP][CLKS_LOG_LINE_MAX];
+static u32 clks_log_journal_head = 0U;
+static u32 clks_log_journal_count_live = 0U;
 
 static const char *clks_log_level_name(enum clks_log_level level) {
     switch (level) {
@@ -50,7 +55,37 @@ static void clks_log_append_hex_u64(char *buffer, usize *cursor, u64 value) {
     }
 }
 
+static void clks_log_journal_copy_line(char *dst, usize dst_size, const char *src) {
+    usize i = 0U;
+
+    if (dst == CLKS_NULL || src == CLKS_NULL || dst_size == 0U) {
+        return;
+    }
+
+    while (i + 1U < dst_size && src[i] != '\0') {
+        dst[i] = src[i];
+        i++;
+    }
+
+    dst[i] = '\0';
+}
+
+static void clks_log_journal_push(const char *line) {
+    if (line == CLKS_NULL) {
+        return;
+    }
+
+    clks_log_journal_copy_line(clks_log_journal[clks_log_journal_head], CLKS_LOG_LINE_MAX, line);
+    clks_log_journal_head = (clks_log_journal_head + 1U) % CLKS_LOG_JOURNAL_CAP;
+
+    if (clks_log_journal_count_live < CLKS_LOG_JOURNAL_CAP) {
+        clks_log_journal_count_live++;
+    }
+}
+
 static void clks_log_emit_line(const char *line) {
+    clks_log_journal_push(line);
+
     clks_serial_write(line);
     clks_serial_write("\n");
 
@@ -93,4 +128,29 @@ void clks_log_hex(enum clks_log_level level, const char *tag, const char *label,
     line[cursor] = '\0';
 
     clks_log_emit_line(line);
+}
+
+u64 clks_log_journal_count(void) {
+    return (u64)clks_log_journal_count_live;
+}
+
+clks_bool clks_log_journal_read(u64 index_from_oldest, char *out_line, usize out_line_size) {
+    u32 oldest;
+    u32 slot;
+
+    if (out_line == CLKS_NULL || out_line_size == 0U) {
+        return CLKS_FALSE;
+    }
+
+    out_line[0] = '\0';
+
+    if (index_from_oldest >= (u64)clks_log_journal_count_live) {
+        return CLKS_FALSE;
+    }
+
+    oldest = (clks_log_journal_head + CLKS_LOG_JOURNAL_CAP - clks_log_journal_count_live) % CLKS_LOG_JOURNAL_CAP;
+    slot = (oldest + (u32)index_from_oldest) % CLKS_LOG_JOURNAL_CAP;
+
+    clks_log_journal_copy_line(out_line, out_line_size, clks_log_journal[slot]);
+    return CLKS_TRUE;
 }