[#597] Add optimizations section into the README.md for code generators

Author: mikir

compiler/extensions/cpp/README.md

@@ -42,6 +42,8 @@ For a **quick start** see the [C++ Tutorial](https://github.com/ndsev/zserio-tut
 
 [Compatibility Check](#compatibility-check)
 
+[Optimizations](#optimizations)
+
 ## Supported C++ Standards
 
 Zserio C++ generator supports the C++11 standard which was published as ISO/IEC 14882:2011.
@@ -409,6 +411,7 @@ a `zserio::CppRuntimeException` during parsing of binary data:
 | Generated Sources | Bitmask constructor | "Value for bitmask [NAME] out of bounds: [VALUE]!" | Throws if value stored in stream is bigger than bitmask upper bound. This could happen only in case of data inconsistency when bitmask value stored in the stream is wrong. |
 | Generated Sources | `valueToEnum` | "Unknown value for enumeration [NAME]: [VALUE]!" | Throws in case of unknown enumeration value. This could happen only in case of data inconsistency when enumeration value stored in the stream is wrong. |
 
+
 ## Compatibility Check
 
 C++ generator honors the `zserio_compatibility_version` specified in the schema. However note that only
@@ -418,3 +421,16 @@ compatibility version and fires an error when it detects any problem.
 
 > Note: Binary encoding of packed arrays has been changed in version `2.5.0` and thus versions `2.4.x` are
 binary incompatible with later versions.
+
+## Optimizations
+
+The C++ generator provides the following optimizations of the generated code:
+
+- If any Zserio structure, choice or union type is not used in the packed array, no packing interface methods
+  will be generated for them
+  (e.g. `write(ZserioPackingContext& context, ::zserio::BitStreamWriter& out)`).
+
+Such optimizations can be done because Zserio relays on the fact that the entire schema is known during the
+generation. Therefore, splitting schema into two parts and generating them independently cannot guarantee
+correct functionality. This can lead to a problem especially for templates, if a template is defined
+in one part and instantiated in the other.

compiler/extensions/java/README.md

@@ -30,6 +30,8 @@ For a **quick start** see the [Java Tutorial](https://github.com/ndsev/zserio-tu
 
 [Compatibility Check](#compatibility-check)
 
+[Optimizations](#optimizations)
+
 ## Supported Java Versions
 
 Zserio Java generator supports the Java SE 8 (LTS), the Java SE 11 (LTS) and the Java SE 17 (LTS).
@@ -133,3 +135,16 @@ compatibility version and fires an error when it detects any problem.
 
 > Note: Binary encoding of packed arrays has been changed in version `2.5.0` and thus versions `2.4.x` are
 binary incompatible with later versions.
+
+## Optimizations
+
+The Java generator provides the following optimizations of the generated code:
+
+- If any Zserio structure, choice or union type is not used in the packed array, no packing interface methods
+  will be generated for them
+  (e.g. `write(zserio.runtime.array.PackingContext context, zserio.runtime.io.BitStreamWriter out)`).
+
+Such optimizations can be done because Zserio relays on the fact that the entire schema is known during the
+generation. Therefore, splitting schema into two parts and generating them independently cannot guarantee
+correct functionality. This can lead to a problem especially for templates, if a template is defined
+in one part and instantiated in the other.

compiler/extensions/python/README.md

@@ -33,6 +33,8 @@ For a **quick start** see the [Python Tutorial](https://github.com/ndsev/zserio-
 
 [Compatibility Check](#compatibility-check)
 
+[Optimizations](#optimizations)
+
 ## Supported Python Versions
 
 Zserio Python generator supports the Python 3.8, 3.9, 3.10, 3.11 and 3.12.
@@ -170,3 +172,15 @@ language features used in the schema are still encoded in a binary compatible wa
 compatibility version and fires an error when it detects any problem.
 
 > Note: Binary encoding of packed arrays has been changed in version `2.5.0`.
+
+## Optimizations
+
+The Python generator provides the following optimizations of the generated code:
+
+- If any Zserio structure, choice or union type is not used in the packed array, no packing interface methods
+  will be generated for them (e.g. `write_packed(self, zserio_context, zserio_writer)`).
+
+Such optimizations can be done because Zserio relays on the fact that the entire schema is known during the
+generation. Therefore, splitting schema into two parts and generating them independently cannot guarantee
+correct functionality. This can lead to a problem especially for templates, if a template is defined
+in one part and instantiated in the other.