docs: add memory chapter

3 files changed, 75 insertions, 101 deletions

diff --git a/docs/ref/api/memory.md b/docs/ref/api/memory.md
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index 00000000..02748123
--- /dev/null
+++ b/docs/ref/api/memory.md
@@ -0,0 +1,75 @@
+# Memory
+
+Managing {{i:memory}} and {{i:allocations}} is something that every C program has to deal with.
+In the case of _NNG_, it can be more complicated because the underlying platform
+code can provide different allocators that might not be compatible with the use
+system allocator used by `malloc` and `free`.
+
+## Allocate Memory
+
+```c
+void *nng_alloc(size_t size);
+```
+
+The {{i:`nng_alloc`}} function allocates a contiguous memory region of
+at least _size_ bytes, and returns a pointer to it.
+The memory will be 64-bit aligned.
+Note that the memory may have random data in it, just like with `malloc`.
+
+If memory cannot be allocated for any reason, then `NULL` will be returned.
+Applications that experience this should treat this like `NNG_ENOMEM`.
+
+Memory returned by `nng_alloc` can be used to hold message buffers, in which
+case it can be directly passed to [`nng_send`][nng_send] using the flag `NNG_FLAG_ALLOC`.
+Alternatively, it can be freed when no longer needed using [`nng_free`][nng_free].
+
+> [!IMPORTANT]
+> Do not use the system `free` function (or the C++ `delete` operator) to release this memory.
+> On some configurations this may work, but on others it will lead to a crash or
+> other unpredictable behavior.
+
+## Deallocate Memory
+
+```c
+void nng_free(void *ptr, size_t size);
+```
+
+The {{i:`nng_free`}} function deallocates memory previously allocated by [`nng_alloc`][nng_alloc].
+
+The _size_ argument must exactly match the _size_ argument that was supplied to
+`nng_alloc` when the memory was allocated.
+
+## Duplicate String
+
+```c
+char *nng_strdup(const char *src);
+```
+
+The {{i:`nng_strdup`}} duplicates the string _src_ and returns it.
+
+This is logically equivalent to using [`nng_alloc`][nng_alloc]
+to allocate a region of memory of `[c] strlen(s) + 1` bytes, and then
+using `strcpy` to copy the string into the destination before
+returning it.
+
+The returned string should be deallocated with
+[`nng_strfree`][nng_strfree], or may be deallocated using the
+[`nng_free`][nng_free] using the length of the returned string plus
+one (for the `NUL` terminating byte).
+
+## Free String
+
+```c
+void nng_strfree(char *str);
+```
+
+The {{i:`nng_strfree`}} function is a convenience function that
+can be used to deallocate strings allocated with [`nng_strdup`][nng_strdup].
+
+It is effectively the same as `[c] nng_free(strlen(str) + 1)`.
+
+[nng_alloc]: #allocate-memory
+[nng_free]: #deallocate-memory
+[nng_strdup]: #duplicate-string
+[nng_strfree]: #free-string
+[nng_send]: TODO.md
diff --git a/docs/ref/api/util/nng_alloc.md b/docs/ref/api/util/nng_alloc.md
deleted file mode 100644
index 39b7bc2c..00000000
--- a/docs/ref/api/util/nng_alloc.md
+++ /dev/null
@@ -1,47 +0,0 @@
-# nng_alloc
-
-## NAME
-
-nng_alloc --- allocate memory
-
-## SYNOPSIS
-
-```c
-#include <nng/nng.h>
-
-void *nng_alloc(size_t size);
-void nng_free(void *ptr, size_t size);
-```
-
-## DESCRIPTION
-
-The {{i:`nng_alloc`}} function allocates a contiguous memory region of
-at least _size_ bytes.
-The memory will be 64-bit aligned.
-
-The {{i:`nng_free`}} function deallocates {{i:memory}} previously allocated by `nng_alloc`.
-
-Memory returned by `nng_alloc` can be used to hold message buffers, in which
-case it can be directly passed to [`nng_send`][nng_send] using the flag `NNG_FLAG_ALLOC`.
-Alternatively, it can be freed when no longer needed using `nng_free`.
-
-> [!IMPORTANT]
-> Do not use the system `free` function (or the C++ `delete` operator) to release this memory.
-> On some configurations this may work, but on others it will lead to a crash or
-> other unpredictable behavior.
-
-## RETURN VALUES
-
-The `nng_alloc` function returns a pointer to the allocated memory on success,
-and `NULL` otherwise.
-
-## ERRORS
-
-No errors are returned, but if memory cannot be allocated then `NULL` is returned.
-This can reasonably be treated as if an `NNG_ENOMEM` error occurred.
-
-## SEE ALSO
-
-[nng_send][nng_send]
-
-[nng_send]: [TODO.md]
diff --git a/docs/ref/api/util/nng_strdup.md b/docs/ref/api/util/nng_strdup.md
deleted file mode 100644
index 32d3fba2..00000000
--- a/docs/ref/api/util/nng_strdup.md
+++ /dev/null
@@ -1,54 +0,0 @@
-# nng_strdup
-
-## NAME
-
-nng_strdup --- duplicate string
-
-## SYNOPSIS
-
-```c
-#include <nng/nng.h>
-
-char *nng_strdup(const char *src);
-void nng_strfree(char *str);
-```
-
-## DESCRIPTION
-
-The {{i:`nng_strdup`}} duplicates the string _src_ and returns it.
-
-This is logically equivalent to using [`nng_alloc`][nng_alloc]
-to allocate a region of memory of `strlen(s) + 1` bytes, and then
-using `strcpy` to copy the string into the destination before
-returning it.
-
-The returned string should be deallocated with
-{{i:`nng_strfree`}}, or may be deallocated using the
-[`nng_free`][nng_free] using the length of the returned string plus
-one (for the `NUL` terminating byte).
-
-> [!IMPORTANT]
-> Do not use the system `free` or similar functions to deallocate
-> the string, since those may use a different memory arena!
-
-> [!IMPORTANT]
-> If a string created with
-> `nng_strdup` is modified to be shorter, then it is incorrect to free it with `nng_strfree`.
-> (The [`nng_free`][nng_free] function can be used instead in that
-> case, using the length of the original string plus one to account for the `NUL` byte, for the size.)
-
-## RETURN VALUES
-
-The `nng_strdup` function returns the new string on success, and `NULL` on failure.
-
-## ERRORS
-
-No errors are returned from `nng_strdup`, but a `NULL` return value should be
-treated the same as `NNG_ENOMEM`.
-
-## SEE ALSO
-
-[nng_alloc][nng_alloc]
-
-[nng_alloc]: ../util/nng_alloc.md
-[nng_free]: ../util/nng_alloc.md