nng message header converted to mdbook

12 files changed, 122 insertions, 396 deletions

diff --git a/docs/man/libnng.3.adoc b/docs/man/libnng.3.adoc
index e13ddf0b..7f1850cc 100644
--- a/docs/man/libnng.3.adoc
+++ b/docs/man/libnng.3.adoc
@@ -99,20 +99,20 @@ Most applications will only interact with the body.
 
 |===
 // |xref:nng_msg_alloc.3.adoc[nng_msg_alloc()]|allocate a message
-|xref:nng_msg_append.3.adoc[nng_msg_append()]|append to message body
-|xref:nng_msg_body.3.adoc[nng_msg_body()]|return message body
+// |xref:nng_msg_append.3.adoc[nng_msg_append()]|append to message body
+// |xref:nng_msg_body.3.adoc[nng_msg_body()]|return message body
 // |xref:nng_msg_capacity.3.adoc[nng_msg_capacity()]|return capacity allocated for message body
-|xref:nng_msg_chop.3.adoc[nng_msg_chop()]|remove data from end of message body
-|xref:nng_msg_clear.3.adoc[nng_msg_clear()]|clear message body
+// |xref:nng_msg_chop.3.adoc[nng_msg_chop()]|remove data from end of message body
+// |xref:nng_msg_clear.3.adoc[nng_msg_clear()]|clear message body
 // |xref:nng_msg_dup.3.adoc[nng_msg_dup()]|duplicate a message
 // |xref:nng_msg_free.3.adoc[nng_msg_free()]|free a message
 |xref:nng_msg_get_pipe.3.adoc[nng_msg_get_pipe()]|get pipe for message
-|xref:nng_msg_insert.3.adoc[nng_msg_insert()]|prepend to message body
-|xref:nng_msg_len.3.adoc[nng_msg_len()]|return the message body length
+// |xref:nng_msg_insert.3.adoc[nng_msg_insert()]|prepend to message body
+// |xref:nng_msg_len.3.adoc[nng_msg_len()]|return the message body length
 // |xref:nng_msg_realloc.3.adoc[nng_msg_realloc()]|reallocate a message
 // |xref:nng_msg_reserve.3.adoc[nng_msg_reserve()]|reserve storage for message body
 |xref:nng_msg_set_pipe.3.adoc[nng_msg_set_pipe()]|set pipe for message
-|xref:nng_msg_trim.3.adoc[nng_msg_trim()]|remove data from start of message body
+// |xref:nng_msg_trim.3.adoc[nng_msg_trim()]|remove data from start of message body
 |xref:nng_recvmsg.3.adoc[nng_recvmsg()]|receive a message
 |xref:nng_sendmsg.3.adoc[nng_sendmsg()]|send a message
 |===
diff --git a/docs/man/nng_msg_append.3.adoc b/docs/man/nng_msg_append.3.adoc
deleted file mode 100644
index 9ed3741d..00000000
--- a/docs/man/nng_msg_append.3.adoc
+++ /dev/null
@@ -1,58 +0,0 @@
-= nng_msg_append(3)
-//
-// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This document is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-== NAME
-
-nng_msg_append - append to message body
-
-== SYNOPSIS
-
-[source, c]
-----
-#include <nng/nng.h>
-
-int nng_msg_append(nng_msg *msg, const void *val, size_t size);
-int nng_msg_append_u16(nng_msg *msg, uint16_t val16);
-int nng_msg_append_u32(nng_msg *msg, uint32_t val32);
-int nng_msg_append_u64(nng_msg *msg, uint64_t val64);
-----
-
-== DESCRIPTION
-
-The `nng_msg_append()` family of functions appends data to
-the end of the body of message _msg_, reallocating it if necessary.
-The first function appends _size_ bytes, copying them from _val_.
-The remaining functions append the value specified (such as _val32_) in
-network-byte order (big-endian).
-
-== RETURN VALUES
-
-These functions return 0 on success, and non-zero otherwise.
-
-== ERRORS
-
-[horizontal]
-`NNG_ENOMEM`:: Insufficient free memory exists.
-
-== SEE ALSO
-
-[.text-left]
-xref:nng_msg_alloc.3.adoc[nng_msg_alloc(3)],
-xref:nng_msg_body.3.adoc[nng_msg_body(3)],
-xref:nng_msg_chop.3.adoc[nng_msg_chop(3)],
-xref:nng_msg_free.3.adoc[nng_msg_free(3)],
-xref:nng_msg_insert.3.adoc[nng_msg_insert(3)],
-xref:nng_msg_len.3.adoc[nng_msg_len(3)],
-xref:nng_msg_realloc.3.adoc[nng_msg_realloc(3)],
-xref:nng_msg_trim.3.adoc[nng_msg_trim(3)],
-xref:nng_strerror.3.adoc[nng_strerror(3)],
-xref:nng_msg.5.adoc[nng_msg(5)],
-xref:nng.7.adoc[nng(7)]
diff --git a/docs/man/nng_msg_body.3.adoc b/docs/man/nng_msg_body.3.adoc
deleted file mode 100644
index ad0fa7b3..00000000
--- a/docs/man/nng_msg_body.3.adoc
+++ /dev/null
@@ -1,62 +0,0 @@
-= nng_msg_body(3)
-//
-// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This document is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-== NAME
-
-nng_msg_body - return message body
-
-== SYNOPSIS
-
-[source, c]
-----
-#include <nng/nng.h>
-
-void *nng_msg_body(nng_msg *msg);
-----
-
-== DESCRIPTION
-
-The `nng_msg_body()` function returns a pointer to the start of the body
-content of the message _msg_.
-
-NOTE: The value returned by this is invalidated by a call to any of the
-functions that modify the message itself.
-Such functions are
-xref:nng_msg_free.3.adoc[`nng_msg_free()`],
-xref:nng_msg_realloc.3.adoc[`nng_msg_realloc()`],
-any of the xref:nng_msg_trim.3.adoc[`nng_msg_trim()`],
-xref:nng_msg_chop.3.adoc[`nng_msg_chop()`],
-xref:nng_msg_append.3.adoc[`nng_msg_append()`],
-or xref:nng_msg_insert.3.adoc[`nng_msg_insert()`] variants.
-
-== RETURN VALUES
-
-Pointer to start of message body.
-
-== ERRORS
-
-None.
-
-== SEE ALSO
-
-[.text-left]
-xref:nng_msg_alloc.3.adoc[nng_msg_alloc(3)],
-xref:nng_msg_append.3.adoc[nng_msg_append(3)],
-xref:nng_msg_chop.3.adoc[nng_msg_chop(3)],
-xref:nng_msg_free.3.adoc[nng_msg_free(3)],
-xref:nng_msg_insert.3.adoc[nng_msg_insert(3)],
-xref:nng_msg_len.3.adoc[nng_msg_len(3)],
-xref:nng_msg_capacity.3.adoc[nng_msg_capacity(3)],
-xref:nng_msg_reserve.3.adoc[nng_msg_reserve(3)],
-xref:nng_msg_realloc.3.adoc[nng_msg_realloc(3)],
-xref:nng_msg_trim.3.adoc[nng_msg_trim(3)],
-xref:nng_msg.5.adoc[nng_msg(5)],
-xref:nng.7.adoc[nng(7)]
diff --git a/docs/man/nng_msg_chop.3.adoc b/docs/man/nng_msg_chop.3.adoc
deleted file mode 100644
index b945f0bb..00000000
--- a/docs/man/nng_msg_chop.3.adoc
+++ /dev/null
@@ -1,61 +0,0 @@
-= nng_msg_chop(3)
-//
-// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This document is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-== NAME
-
-nng_msg_chop - remove data from end of message body
-
-== SYNOPSIS
-
-[source, c]
-----
-#include <nng/nng.h>
-
-int nng_msg_chop(nng_msg *msg, size_t size);
-int nng_msg_chop_u16(nng_msg *msg, uint16_t *val16);
-int nng_msg_chop_u32(nng_msg *msg, uint32_t *val32);
-int nng_msg_chop_u64(nng_msg *msg, uint64_t *val64);
-----
-
-== DESCRIPTION
-
-The `nng_msg_chop()` family of functions removes data from
-the end of the body of message _msg_.
-The first function removes _size_ bytes.
-The remaining functions remove 2, 4, or 8 bytes, and stores them in the value
-(such as _val32_),
-after converting them from network-byte order (big-endian) to native byte order.
-
-== RETURN VALUES
-
-These functions return 0 on success, and non-zero otherwise.
-
-== ERRORS
-
-[horizontal]
-`NNG_EINVAL`:: The message body is too short to remove the requested data.
-
-== SEE ALSO
-
-[.text-left]
-xref:nng_msg_alloc.3.adoc[nng_msg_alloc(3)],
-xref:nng_msg_append.3.adoc[nng_msg_append(3)],
-xref:nng_msg_body.3.adoc[nng_msg_body(3)],
-xref:nng_msg_free.3.adoc[nng_msg_free(3)],
-xref:nng_msg_insert.3.adoc[nng_msg_insert(3)],
-xref:nng_msg_len.3.adoc[nng_msg_len(3)],
-xref:nng_msg_capacity.3.adoc[nng_msg_capacity(3)],
-xref:nng_msg_reserve.3.adoc[nng_msg_reserve(3)],
-xref:nng_msg_realloc.3.adoc[nng_msg_realloc(3)],
-xref:nng_msg_trim.3.adoc[nng_msg_trim(3)],
-xref:nng_strerror.3.adoc[nng_strerror(3)],
-xref:nng_msg.5.adoc[nng_msg(5)],
-xref:nng.7.adoc[nng(7)]
diff --git a/docs/man/nng_msg_clear.3.adoc b/docs/man/nng_msg_clear.3.adoc
deleted file mode 100644
index e5b3bf47..00000000
--- a/docs/man/nng_msg_clear.3.adoc
+++ /dev/null
@@ -1,41 +0,0 @@
-= nng_msg_clear(3)
-//
-// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This document is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-== NAME
-
-nng_msg_clear - clear message body content
-
-== SYNOPSIS
-
-[source, c]
-----
-#include <nng/nng.h>
-
-void nng_msg_clear(nng_msg *msg);
-----
-
-== DESCRIPTION
-
-The `nng_msg_clear()` function resets the body length of _msg_ to zero.
-
-== RETURN VALUES
-
-None.
-
-== ERRORS
-
-None.
-
-== SEE ALSO
-
-[.text-left]
-xref:nng_msg.5.adoc[nng_msg(5)],
-xref:nng.7.adoc[nng(7)]
diff --git a/docs/man/nng_msg_insert.3.adoc b/docs/man/nng_msg_insert.3.adoc
deleted file mode 100644
index 25f98fce..00000000
--- a/docs/man/nng_msg_insert.3.adoc
+++ /dev/null
@@ -1,63 +0,0 @@
-= nng_msg_insert(3)
-//
-// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This document is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-== NAME
-
-nng_msg_insert - prepend to message body
-
-== SYNOPSIS
-
-[source, c]
-----
-#include <nng/nng.h>
-
-int nng_msg_insert(nng_msg *msg, const void *val, size_t size);
-int nng_msg_insert_u16(nng_msg *msg, uint16_t val16);
-int nng_msg_insert_u32(nng_msg *msg, uint32_t val32);
-int nng_msg_insert_u64(nng_msg *msg, uint64_t val64);
-----
-
-== DESCRIPTION
-
-The `nng_msg_insert()` family of functions prepends data to
-the front of the body of message _msg_, reallocating it if necessary.
-The first function prepends _size_ bytes, copying them from _val_.
-The remaining functions prepend the specified value (such as _val32_)
-in network-byte order (big-endian).
-
-TIP: These functions make use of space pre-allocated in front of the
-message body if available, so they can often avoid performing any reallocation.
-Applications should use these instead of reallocating and copying message
-content themselves, in order to benefit from this capability.
-
-== RETURN VALUES
-
-These functions return 0 on success, and non-zero otherwise.
-
-== ERRORS
-
-[horizontal]
-`NNG_ENOMEM`:: Insufficient free memory exists.
-
-== SEE ALSO
-
-[.text-left]
-xref:nng_msg_alloc.3.adoc[nng_msg_alloc(3)],
-xref:nng_msg_append.3.adoc[nng_msg_append(3)],
-xref:nng_msg_body.3.adoc[nng_msg_body(3)],
-xref:nng_msg_chop.3.adoc[nng_msg_chop(3)],
-xref:nng_msg_free.3.adoc[nng_msg_free(3)],
-xref:nng_msg_len.3.adoc[nng_msg_len(3)],
-xref:nng_msg_realloc.3.adoc[nng_msg_realloc(3)],
-xref:nng_msg_trim.3.adoc[nng_msg_trim(3)],
-xref:nng_strerror.3.adoc[nng_strerror(3)],
-xref:nng_msg.5.adoc[nng_msg(5)],
-xref:nng.7.adoc[nng(7)]
diff --git a/docs/man/nng_msg_len.3.adoc b/docs/man/nng_msg_len.3.adoc
deleted file mode 100644
index 2a3dfe67..00000000
--- a/docs/man/nng_msg_len.3.adoc
+++ /dev/null
@@ -1,43 +0,0 @@
-= nng_msg_len(3)
-//
-// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This document is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-== NAME
-
-nng_msg_len - return message body length
-
-== SYNOPSIS
-
-[source, c]
-----
-#include <nng/nng.h>
-
-size_t nng_msg_len(nng_msg *msg);
-----
-
-== DESCRIPTION
-
-The `nng_msg_len()` returns the length of the body of message _msg_.
-
-== RETURN VALUES
-
-Length of message body.
-
-== ERRORS
-
-None.
-
-== SEE ALSO
-
-[.text-left]
-xref:nng_msg_alloc.3.adoc[nng_msg_alloc(3)],
-xref:nng_msg_body.3.adoc[nng_msg_body(3)],
-xref:nng_msg.5.adoc[nng_msg(5)],
-xref:nng.7.adoc[nng(7)]
diff --git a/docs/man/nng_msg_trim.3.adoc b/docs/man/nng_msg_trim.3.adoc
deleted file mode 100644
index aa482958..00000000
--- a/docs/man/nng_msg_trim.3.adoc
+++ /dev/null
@@ -1,60 +0,0 @@
-= nng_msg_trim(3)
-//
-// Copyright 2018 Staysail Systems, Inc. <info@staysail.tech>
-// Copyright 2018 Capitar IT Group BV <info@capitar.com>
-//
-// This document is supplied under the terms of the MIT License, a
-// copy of which should be located in the distribution where this
-// file was obtained (LICENSE.txt).  A copy of the license may also be
-// found online at https://opensource.org/licenses/MIT.
-//
-
-== NAME
-
-nng_msg_trim - remove data from start of message body
-
-== SYNOPSIS
-
-[source, c]
-----
-#include <nng/nng.h>
-
-int nng_msg_trim(nng_msg *msg, size_t size);
-int nng_msg_trim_u16(nng_msg *msg, uint16_t *val16);
-int nng_msg_trim_u32(nng_msg *msg, uint32_t *val32);
-int nng_msg_trim_u64(nng_msg *msg, uint64_t *val64);
-----
-
-== DESCRIPTION
-
-The `nng_msg_trim()` family of functions removes data from
-the start of the body of message _msg_.
-The first function removes _size_ bytes.
-The remaining functions remove 2, 4, or 8 bytes, and stores them in the value
-(such as _val32_),
-after converting them from network-byte order (big-endian) to native
-byte order.
-
-== RETURN VALUES
-
-These functions return 0 on success, and non-zero otherwise.
-
-== ERRORS
-
-[horizontal]
-`NNG_EINVAL`:: The message body is too short to remove the requested data.
-
-== SEE ALSO
-
-[.text-left]
-xref:nng_msg_alloc.3.adoc[nng_msg_alloc(3)],
-xref:nng_msg_append.3.adoc[nng_msg_append(3)],
-xref:nng_msg_body.3.adoc[nng_msg_body(3)],
-xref:nng_msg_chop.3.adoc[nng_msg_chop(3)],
-xref:nng_msg_free.3.adoc[nng_msg_free(3)],
-xref:nng_msg_insert.3.adoc[nng_msg_insert(3)],
-xref:nng_msg_len.3.adoc[nng_msg_len(3)],
-xref:nng_msg_realloc.3.adoc[nng_msg_realloc(3)],
-xref:nng_strerror.3.adoc[nng_strerror(3)],
-xref:nng_msg.5.adoc[nng_msg(5)],
-xref:nng.7.adoc[nng(7)]
diff --git a/docs/ref/SUMMARY.md b/docs/ref/SUMMARY.md
index 7e9bcc2d..0415cad8 100644
--- a/docs/ref/SUMMARY.md
+++ b/docs/ref/SUMMARY.md
@@ -5,6 +5,7 @@
   - [Messages](./api/msg/index.md)
 
     - [nng_msg](./api/msg/nng_msg.md)
+    - [nng_msg_body](./api/msg/nng_msg_body.md)
 
   - [Threading and Synchronization](./api/thr/index.md)
 
diff --git a/docs/ref/api/msg/index.md b/docs/ref/api/msg/index.md
index 18a3f620..5772cec8 100644
--- a/docs/ref/api/msg/index.md
+++ b/docs/ref/api/msg/index.md
@@ -3,3 +3,4 @@
 These interfaces deal with messages, used in the Scalability Protocols.
 
 - [nng_msg](./nng_msg.md) --- message
+- [nng_msg_body](./nng_msg_body.md) --- message body
diff --git a/docs/ref/api/msg/nng_msg.md b/docs/ref/api/msg/nng_msg.md
index 84d6c273..8d8b8686 100644
--- a/docs/ref/api/msg/nng_msg.md
+++ b/docs/ref/api/msg/nng_msg.md
@@ -87,7 +87,7 @@ by making use of scratch areas at the beginning and end of the message.
 These scratch areas, the "{{i:headroom}}" and "{{i:tailroom}}", are automatically
 included when allocating a message.
 
-Using `nng_msg_reserve` to ensure that adequate buffer space is availabe
+Using `nng_msg_reserve` to ensure that adequate buffer space is available
 in advance can reduce repeated allocations and data copies when modifying messages.
 
 ## RETURN VALUES
diff --git a/docs/ref/api/msg/nng_msg_body.md b/docs/ref/api/msg/nng_msg_body.md
new file mode 100644
index 00000000..ff78e852
--- /dev/null
+++ b/docs/ref/api/msg/nng_msg_body.md
@@ -0,0 +1,112 @@
+# nng_msg_body
+
+## NAME
+
+nng_msg_body --- message body
+
+## SYNOPSIS
+
+```c
+#include <nng/nng.h>
+
+void *nng_msg_body(nng_msg *msg);
+size_t nng_msg_len(nng_msg *msg);
+void nng_msg_clear(nng_msg *msg);
+int nng_msg_append(nng_msg *msg, const void *val, size_t size);
+int nng_msg_append_u16(nng_msg *msg, uint16_t val16);
+int nng_msg_append_u32(nng_msg *msg, uint32_t val32);
+int nng_msg_append_u64(nng_msg *msg, uint64_t val64);
+int nng_msg_insert(nng_msg *msg, const void *val, size_t size);
+int nng_msg_insert_u16(nng_msg *msg, uint16_t val16);
+int nng_msg_insert_u32(nng_msg *msg, uint32_t val32);
+int nng_msg_insert_u64(nng_msg *msg, uint64_t val64);
+int nng_msg_chop(nng_msg *msg, size_t size);
+int nng_msg_chop_u16(nng_msg *msg, uint16_t *val16);
+int nng_msg_chop_u32(nng_msg *msg, uint32_t *val32);
+int nng_msg_chop_u64(nng_msg *msg, uint64_t *val64);
+int nng_msg_trim(nng_msg *msg, size_t size);
+int nng_msg_trim_u16(nng_msg *msg, uint16_t *val16);
+int nng_msg_trim_u32(nng_msg *msg, uint32_t *val32);
+int nng_msg_trim_u64(nng_msg *msg, uint64_t *val64);
+```
+
+## DESCRIPTION
+
+The {{i:body}} of a message is the part of the message that is used
+for the application payload, and does not normally include protocol
+or transport-specific data.
+
+The `nng_msg_body` function returns a pointer to the start of the body
+content of the message _msg_.
+
+The `nng_msg_len` function returns the length of the message body in bytes.
+
+> [!IMPORTANT]
+> The value returned by `nng_msg_body` is invalidated by a call to any of the
+> functions that modify the message itself.
+
+The rest of these functions allow modifying the message body.
+
+### Clearing the Message Body
+
+The message body can be entirely cleared using {{i:`nng_msg_clear`}}.
+The underlying buffers are left intact, and the bytes may remain at their original values, so
+this function should not be relied upon for zeroizing sensitive data.
+
+### Appending and Inserting Data
+
+Appending data to a message body is done by using the {{i:`nng_msg_append`}} functions.
+The base `nng_msg_append` function appends _size_ bytes of untyped data to the end of the
+message.
+
+> [!TIP]
+> Using [`nng_msg_reserve`][nng_msg] to preallocate space before appending or inserting
+> can reduce allocations and data copies, for a significant performance benefit.
+
+Use of the typed versions, ending in suffixes `_u16`, `_u32`, and `_u64` allows
+for unsigned integers to be appended directly. The integers are encoded in network byte order, with
+the most significant byte appearing first. The message body will by two, four, or eight
+bytes accordingly.
+
+Data may inserted before the rest of the message body by using the {{i:`nng_msg_insert`}} functions.
+This will attempt to use "headroom" in the message to avoid a data copy.
+
+> [!TIP]
+> Message headroom is limited, so `nng_msg_insert` is best used sparingly.
+> It is much more efficient to build the message content from start to end
+> using `nng_msg_append`.
+
+Typed versions and the untyped base function behave similarly to the `nng_msg_append` functions.
+
+### Consuming Data
+
+The {{i:`nng_msg_trim`}} functions remove data from the beginning of the message body.
+This is accomplished by incrementing the pointer to start of the message by the appropriate size.
+
+Additionally, functions with typed suffixes (`_u16`, `_u32`, `_u64`) allow the data obtained to be decoded and returned.
+The data is assumed to have been in network byte order in the message, but is returned in
+the native machine byte order. The appropriate number of bytes is consumed for each of these types,
+so two bytes for `_u16`, four bytes for `_u32`, and eight bytes for `_u64`.
+
+The {{i:`nng_msg_chop`}} functions behave in a similar fashion, but consume data from the
+end of the message body.
+
+## RETURN VALUES
+
+The `nng_msg_body` function returns a pointer to the start of the message body.
+The `nng_msg_len` function returns the length of the message in bytes.
+The `nng_msg_clear` function does not return anything.
+The remaining functions return zero on success, or a non-zero error value on failure.
+
+## ERRORS
+
+- `NNG_ENOMEM`: Insufficient memory exists to grow the message.
+- `NNG_EINVAL`: The message body is too short to remove the requested data.
+
+## SEE ALSO
+
+[nng_msg][nng_msg],
+[nng_msg_header][nng_msg_header]
+
+[nng_msg]: ./nng_msg.md
+[nng_msg_header]: ./nng_msg_header.md