diff --git a/objectivec/GPBCodedInputStream.h b/objectivec/GPBCodedInputStream.h
index 42a0494..fbe5009 100644
--- a/objectivec/GPBCodedInputStream.h
+++ b/objectivec/GPBCodedInputStream.h
@@ -35,52 +35,218 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
-// Reads and decodes protocol message fields.
-// Subclassing of GPBCodedInputStream is NOT supported.
+CF_EXTERN_C_BEGIN
+
+/**
+ * @c GPBCodedInputStream exception name. Exceptions raised from
+ * @c GPBCodedInputStream contain an underlying error in the userInfo dictionary
+ * under the GPBCodedInputStreamUnderlyingErrorKey key.
+ **/
+extern NSString *const GPBCodedInputStreamException;
+
+/** The key under which the underlying NSError from the exception is stored. */
+extern NSString *const GPBCodedInputStreamUnderlyingErrorKey;
+
+/** NSError domain used for @c GPBCodedInputStream errors. */
+extern NSString *const GPBCodedInputStreamErrorDomain;
+
+/**
+ * Error code for NSError with @c GPBCodedInputStreamErrorDomain.
+ **/
+typedef NS_ENUM(NSInteger, GPBCodedInputStreamErrorCode) {
+  /** The size does not fit in the remaining bytes to be read. */
+  GPBCodedInputStreamErrorInvalidSize = -100,
+  /** Attempted to read beyond the subsection limit. */
+  GPBCodedInputStreamErrorSubsectionLimitReached = -101,
+  /** The requested subsection limit is invalid. */
+  GPBCodedInputStreamErrorInvalidSubsectionLimit = -102,
+  /** Invalid tag read. */
+  GPBCodedInputStreamErrorInvalidTag = -103,
+  /** Invalid UTF-8 character in a string. */
+  GPBCodedInputStreamErrorInvalidUTF8 = -104,
+  /** Invalid VarInt read. */
+  GPBCodedInputStreamErrorInvalidVarInt = -105,
+  /** The maximum recursion depth of messages was exceeded. */
+  GPBCodedInputStreamErrorRecursionDepthExceeded = -106,
+};
+
+CF_EXTERN_C_END
+
+/**
+ * Reads and decodes protocol message fields.
+ *
+ * The common uses of protocol buffers shouldn't need to use this class.
+ * @c GPBMessage's provide a @c +parseFromData:error: and
+ * @c +parseFromData:extensionRegistry:error: method that will decode a
+ * message for you.
+ *
+ * @note Subclassing of @c GPBCodedInputStream is NOT supported.
+ **/
 @interface GPBCodedInputStream : NSObject
 
+/**
+ * Creates a new stream wrapping some data.
+ *
+ * @param data The data to wrap inside the stream.
+ *
+ * @return A newly instanced GPBCodedInputStream.
+ **/
 + (instancetype)streamWithData:(NSData *)data;
+
+/**
+ * Initializes a stream wrapping some data.
+ *
+ * @param data The data to wrap inside the stream.
+ *
+ * @return A newly initialized GPBCodedInputStream.
+ **/
 - (instancetype)initWithData:(NSData *)data;
 
-// Attempt to read a field tag, returning zero if we have reached EOF.
-// Protocol message parsers use this to read tags, since a protocol message
-// may legally end wherever a tag occurs, and zero is not a valid tag number.
+/**
+ * Attempts to read a field tag, returning zero if we have reached EOF.
+ * Protocol message parsers use this to read tags, since a protocol message
+ * may legally end wherever a tag occurs, and zero is not a valid tag number.
+ *
+ * @return The field tag, or zero if EOF was reached.
+ **/
 - (int32_t)readTag;
 
+/**
+ * @return A double read from the stream.
+ **/
 - (double)readDouble;
+/**
+ * @return A float read from the stream.
+ **/
 - (float)readFloat;
+/**
+ * @return A uint64 read from the stream.
+ **/
 - (uint64_t)readUInt64;
+/**
+ * @return A uint32 read from the stream.
+ **/
 - (uint32_t)readUInt32;
+/**
+ * @return An int64 read from the stream.
+ **/
 - (int64_t)readInt64;
+/**
+ * @return An int32 read from the stream.
+ **/
 - (int32_t)readInt32;
+/**
+ * @return A fixed64 read from the stream.
+ **/
 - (uint64_t)readFixed64;
+/**
+ * @return A fixed32 read from the stream.
+ **/
 - (uint32_t)readFixed32;
+/**
+ * @return An enum read from the stream.
+ **/
 - (int32_t)readEnum;
+/**
+ * @return A sfixed32 read from the stream.
+ **/
 - (int32_t)readSFixed32;
+/**
+ * @return A fixed64 read from the stream.
+ **/
 - (int64_t)readSFixed64;
+/**
+ * @return A sint32 read from the stream.
+ **/
 - (int32_t)readSInt32;
+/**
+ * @return A sint64 read from the stream.
+ **/
 - (int64_t)readSInt64;
+/**
+ * @return A boolean read from the stream.
+ **/
 - (BOOL)readBool;
+/**
+ * @return A string read from the stream.
+ **/
 - (NSString *)readString;
+/**
+ * @return Data read from the stream.
+ **/
 - (NSData *)readBytes;
 
-// Read an embedded message field value from the stream.
+/**
+ * Read an embedded message field value from the stream.
+ *
+ * @param message           The message to set fields on as they are read.
+ * @param extensionRegistry An optional extension registry to use to lookup
+ *                          extensions for message.
+ **/
 - (void)readMessage:(GPBMessage *)message
-    extensionRegistry:(nullable GPBExtensionRegistry *)extensionRegistry;
+  extensionRegistry:(nullable GPBExtensionRegistry *)extensionRegistry;
 
-// Reads and discards a single field, given its tag value. Returns NO if the
-// tag is an endgroup tag, in which case nothing is skipped.  Otherwise,
-// returns YES.
+/**
+ * Reads and discards a single field, given its tag value.
+ *
+ * @param tag The tag number of the field to skip.
+ *
+ * @return NO if the tag is an endgroup tag (in which case nothing is skipped),
+ *         YES in all other cases.
+ **/
 - (BOOL)skipField:(int32_t)tag;
 
-// Reads and discards an entire message.  This will read either until EOF
-// or until an endgroup tag, whichever comes first.
+/**
+ * Reads and discards an entire message. This will read either until EOF or
+ * until an endgroup tag, whichever comes first.
+ **/
 - (void)skipMessage;
 
-// Verifies that the last call to readTag() returned the given tag value.
-// This is used to verify that a nested group ended with the correct end tag.
-// Throws NSParseErrorException if value does not match the last tag.
-- (void)checkLastTagWas:(int32_t)value;
+/**
+ * Check to see if the logical end of the stream has been reached.
+ *
+ * @note This can return NO when there is no more data, but the current parsing
+ *       expected more data.
+ *
+ * @return YES if the logical end of the stream has been reached, NO otherwise.
+ **/
+- (BOOL)isAtEnd;
+
+/**
+ * @return The offset into the stream.
+ **/
+- (size_t)position;
+
+/**
+ * Moves the limit to the given byte offset starting at the current location.
+ *
+ * @exception GPBCodedInputStreamException If the requested bytes exceeed the
+ *            current limit.
+ *
+ * @param byteLimit The number of bytes to move the limit, offset to the current
+ *                  location.
+ *
+ * @return The limit offset before moving the new limit.
+ */
+- (size_t)pushLimit:(size_t)byteLimit;
+
+/**
+ * Moves the limit back to the offset as it was before calling pushLimit:.
+ *
+ * @param oldLimit The number of bytes to move the current limit. Usually this
+ *                 is the value returned by the pushLimit: method.
+ */
+- (void)popLimit:(size_t)oldLimit;
+
+/**
+ * Verifies that the last call to -readTag returned the given tag value. This
+ * is used to verify that a nested group ended with the correct end tag.
+ *
+ * @exception NSParseErrorException If the value does not match the last tag.
+ *
+ * @param expected The tag that was expected.
+ **/
+- (void)checkLastTagWas:(int32_t)expected;
 
 @end