Extents: Split out introspection functionality.

This isn't really part of the core extent allocation facilities.  Especially as
this module grows, having it in its own place may come in handy.

src/inspect.c

@@ -0,0 +1,77 @@
+#include "jemalloc/internal/jemalloc_preamble.h"
+#include "jemalloc/internal/jemalloc_internal_includes.h"
+
+void
+inspect_extent_util_stats_get(tsdn_t *tsdn, const void *ptr, size_t *nfree,
+    size_t *nregs, size_t *size) {
+	assert(ptr != NULL && nfree != NULL && nregs != NULL && size != NULL);
+
+	const extent_t *extent = iealloc(tsdn, ptr);
+	if (unlikely(extent == NULL)) {
+		*nfree = *nregs = *size = 0;
+		return;
+	}
+
+	*size = extent_size_get(extent);
+	if (!extent_slab_get(extent)) {
+		*nfree = 0;
+		*nregs = 1;
+	} else {
+		*nfree = extent_nfree_get(extent);
+		*nregs = bin_infos[extent_szind_get(extent)].nregs;
+		assert(*nfree <= *nregs);
+		assert(*nfree * extent_usize_get(extent) <= *size);
+	}
+}
+
+void
+inspect_extent_util_stats_verbose_get(tsdn_t *tsdn, const void *ptr,
+    size_t *nfree, size_t *nregs, size_t *size, size_t *bin_nfree,
+    size_t *bin_nregs, void **slabcur_addr) {
+	assert(ptr != NULL && nfree != NULL && nregs != NULL && size != NULL
+	    && bin_nfree != NULL && bin_nregs != NULL && slabcur_addr != NULL);
+
+	const extent_t *extent = iealloc(tsdn, ptr);
+	if (unlikely(extent == NULL)) {
+		*nfree = *nregs = *size = *bin_nfree = *bin_nregs = 0;
+		*slabcur_addr = NULL;
+		return;
+	}
+
+	*size = extent_size_get(extent);
+	if (!extent_slab_get(extent)) {
+		*nfree = *bin_nfree = *bin_nregs = 0;
+		*nregs = 1;
+		*slabcur_addr = NULL;
+		return;
+	}
+
+	*nfree = extent_nfree_get(extent);
+	const szind_t szind = extent_szind_get(extent);
+	*nregs = bin_infos[szind].nregs;
+	assert(*nfree <= *nregs);
+	assert(*nfree * extent_usize_get(extent) <= *size);
+
+	const arena_t *arena = (arena_t *)atomic_load_p(
+	    &arenas[extent_arena_ind_get(extent)], ATOMIC_RELAXED);
+	assert(arena != NULL);
+	const unsigned binshard = extent_binshard_get(extent);
+	bin_t *bin = &arena->bins[szind].bin_shards[binshard];
+
+	malloc_mutex_lock(tsdn, &bin->lock);
+	if (config_stats) {
+		*bin_nregs = *nregs * bin->stats.curslabs;
+		assert(*bin_nregs >= bin->stats.curregs);
+		*bin_nfree = *bin_nregs - bin->stats.curregs;
+	} else {
+		*bin_nfree = *bin_nregs = 0;
+	}
+	extent_t *slab;
+	if (bin->slabcur != NULL) {
+		slab = bin->slabcur;
+	} else {
+		slab = extent_heap_first(&bin->slabs_nonfull);
+	}
+	*slabcur_addr = slab != NULL ? extent_addr_get(slab) : NULL;
+	malloc_mutex_unlock(tsdn, &bin->lock);
+}