diff --git a/data/test_types.desc b/data/test_types.desc
new file mode 100644
index 0000000..6ff3fb1
Binary files /dev/null and b/data/test_types.desc differ
diff --git a/src/lib.rs b/src/lib.rs
index 636c7c1..18ef69e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,3 +1,4 @@
+pub mod proto_gen;
 use std::fmt;
 
 #[derive(Debug, PartialEq, Eq)]
@@ -180,7 +181,7 @@ impl<'a> ProtoAccessor<'a> {
     }
 
     /// Returns the value and wire type of the last occurrence of the specified field.
-    pub fn get_value(&self, field_number: u32) -> Result<(&[u8], WireType)> {
+    pub fn get_value(&self, field_number: u32) -> Result<(&'a [u8], WireType)> {
         let mut last_value = None;
         for item in self.fields() {
             let (tag, value) = item?;
diff --git a/src/proto_gen/google/protobuf/compiler/plugin.rs b/src/proto_gen/google/protobuf/compiler/plugin.rs
new file mode 100644
index 0000000..2b4dae9
--- /dev/null
+++ b/src/proto_gen/google/protobuf/compiler/plugin.rs
@@ -0,0 +1,281 @@
+use crate::{ProtoAccessor, ProtoBuilder, Result, RotoError};
+use crate::proto_gen::google::protobuf::descriptor::{FileDescriptorProto, GeneratedCodeInfo};
+use std::str;
+
+pub struct Version<'a>(ProtoAccessor<'a>);
+
+impl<'a> Version<'a> {
+    pub fn new(data: &'a [u8]) -> Result<Self> {
+        Ok(Self(ProtoAccessor::new(data)?))
+    }
+
+    pub fn major(&self) -> Result<i32> {
+        let (bytes, _) = self.0.get_value(1)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val as i32)
+    }
+
+    pub fn minor(&self) -> Result<i32> {
+        let (bytes, _) = self.0.get_value(2)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val as i32)
+    }
+
+    pub fn patch(&self) -> Result<i32> {
+        let (bytes, _) = self.0.get_value(3)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val as i32)
+    }
+
+    pub fn suffix(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(4)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn builder(buf: &mut [u8]) -> VersionBuilder<'_> {
+        VersionBuilder {
+            builder: ProtoBuilder::new(buf),
+        }
+    }
+}
+
+pub struct VersionBuilder<'b> {
+    builder: ProtoBuilder<'b>,
+}
+
+impl<'b> VersionBuilder<'b> {
+    pub fn major(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(1, value)?;
+        Ok(self)
+    }
+
+    pub fn minor(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(2, value)?;
+        Ok(self)
+    }
+
+    pub fn patch(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(3, value)?;
+        Ok(self)
+    }
+
+    pub fn suffix(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(4, value)?;
+        Ok(self)
+    }
+
+    pub fn finish(self) -> Result<&'b mut [u8]> {
+        self.builder.finish()
+    }
+}
+
+pub struct CodeGeneratorRequest<'a>(ProtoAccessor<'a>);
+
+impl<'a> CodeGeneratorRequest<'a> {
+    pub fn new(data: &'a [u8]) -> Result<Self> {
+        Ok(Self(ProtoAccessor::new(data)?))
+    }
+
+    pub fn file_to_generate(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(1)
+    }
+
+    pub fn parameter(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(2)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn compiler_version(&self) -> Result<Version<'a>> {
+        let (bytes, _) = self.0.get_value(3)?;
+        Version::new(bytes)
+    }
+
+    pub fn proto_file(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(15)
+    }
+
+    pub fn source_file_descriptors(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(17)
+    }
+
+    pub fn builder(buf: &mut [u8]) -> CodeGeneratorRequestBuilder<'_> {
+        CodeGeneratorRequestBuilder {
+            builder: ProtoBuilder::new(buf),
+        }
+    }
+}
+
+pub struct CodeGeneratorRequestBuilder<'b> {
+    builder: ProtoBuilder<'b>,
+}
+
+impl<'b> CodeGeneratorRequestBuilder<'b> {
+    pub fn add_file_to_generate(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(1, value)?;
+        Ok(self)
+    }
+
+    pub fn parameter(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(2, value)?;
+        Ok(self)
+    }
+
+    pub fn compiler_version(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(3, data)?;
+        Ok(self)
+    }
+
+    pub fn add_proto_file(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(15, data)?;
+        Ok(self)
+    }
+
+    pub fn add_source_file_descriptor(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(17, data)?;
+        Ok(self)
+    }
+
+    pub fn finish(self) -> Result<&'b mut [u8]> {
+        self.builder.finish()
+    }
+}
+
+pub struct CodeGeneratorResponse<'a>(ProtoAccessor<'a>);
+
+impl<'a> CodeGeneratorResponse<'a> {
+    pub fn new(data: &'a [u8]) -> Result<Self> {
+        Ok(Self(ProtoAccessor::new(data)?))
+    }
+
+    pub fn error(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(1)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn supported_features(&self) -> Result<u64> {
+        let (bytes, _) = self.0.get_value(2)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val)
+    }
+
+    pub fn minimum_edition(&self) -> Result<i32> {
+        let (bytes, _) = self.0.get_value(3)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val as i32)
+    }
+
+    pub fn maximum_edition(&self) -> Result<i32> {
+        let (bytes, _) = self.0.get_value(4)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val as i32)
+    }
+
+    pub fn file(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(15)
+    }
+
+    pub fn builder(buf: &mut [u8]) -> CodeGeneratorResponseBuilder<'_> {
+        CodeGeneratorResponseBuilder {
+            builder: ProtoBuilder::new(buf),
+        }
+    }
+}
+
+pub struct CodeGeneratorResponseBuilder<'b> {
+    builder: ProtoBuilder<'b>,
+}
+
+impl<'b> CodeGeneratorResponseBuilder<'b> {
+    pub fn error(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(1, value)?;
+        Ok(self)
+    }
+
+    pub fn supported_features(mut self, value: u64) -> Result<Self> {
+        self.builder.write_varint(2, value)?;
+        Ok(self)
+    }
+
+    pub fn minimum_edition(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(3, value)?;
+        Ok(self)
+    }
+
+    pub fn maximum_edition(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(4, value)?;
+        Ok(self)
+    }
+
+    pub fn add_file(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(15, data)?;
+        Ok(self)
+    }
+
+    pub fn finish(self) -> Result<&'b mut [u8]> {
+        self.builder.finish()
+    }
+}
+
+pub struct CodeGeneratorResponseFile<'a>(ProtoAccessor<'a>);
+
+impl<'a> CodeGeneratorResponseFile<'a> {
+    pub fn new(data: &'a [u8]) -> Result<Self> {
+        Ok(Self(ProtoAccessor::new(data)?))
+    }
+
+    pub fn name(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(1)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn insertion_point(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(2)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn content(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(15)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn generated_code_info(&self) -> Result<GeneratedCodeInfo<'a>> {
+        let (bytes, _) = self.0.get_value(16)?;
+        GeneratedCodeInfo::new(bytes)
+    }
+
+    pub fn builder(buf: &mut [u8]) -> CodeGeneratorResponseFileBuilder<'_> {
+        CodeGeneratorResponseFileBuilder {
+            builder: ProtoBuilder::new(buf),
+        }
+    }
+}
+
+pub struct CodeGeneratorResponseFileBuilder<'b> {
+    builder: ProtoBuilder<'b>,
+}
+
+impl<'b> CodeGeneratorResponseFileBuilder<'b> {
+    pub fn name(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(1, value)?;
+        Ok(self)
+    }
+
+    pub fn insertion_point(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(2, value)?;
+        Ok(self)
+    }
+
+    pub fn content(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(15, value)?;
+        Ok(self)
+    }
+
+    pub fn generated_code_info(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(16, data)?;
+        Ok(self)
+    }
+
+    pub fn finish(self) -> Result<&'b mut [u8]> {
+        self.builder.finish()
+    }
+}
diff --git a/src/proto_gen/google/protobuf/descriptor.rs b/src/proto_gen/google/protobuf/descriptor.rs
new file mode 100644
index 0000000..5598ae4
--- /dev/null
+++ b/src/proto_gen/google/protobuf/descriptor.rs
@@ -0,0 +1,566 @@
+use crate::{ProtoAccessor, ProtoBuilder, Result, RotoError};
+use std::str;
+
+/// The edition of the proto file.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(i32)]
+pub enum Edition {
+    EditionLegacy = 0,
+    EditionProto2 = 1,
+    EditionProto3 = 2,
+    Edition2023 = 3,
+    Edition2024 = 4,
+    Edition2026 = 5,
+}
+
+impl Edition {
+    pub fn from_i32(value: i32) -> Self {
+        match value {
+            1 => Edition::EditionProto2,
+            2 => Edition::EditionProto3,
+            3 => Edition::Edition2023,
+            4 => Edition::Edition2024,
+            5 => Edition::Edition2026,
+            _ => Edition::EditionLegacy,
+        }
+    }
+}
+
+pub struct FileDescriptorSet<'a>(ProtoAccessor<'a>);
+
+impl<'a> FileDescriptorSet<'a> {
+    pub fn new(data: &'a [u8]) -> Result<Self> {
+        Ok(Self(ProtoAccessor::new(data)?))
+    }
+
+    pub fn file(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(1)
+    }
+}
+
+pub struct FileDescriptorProto<'a>(ProtoAccessor<'a>);
+
+impl<'a> FileDescriptorProto<'a> {
+    pub fn new(data: &'a [u8]) -> Result<Self> {
+        Ok(Self(ProtoAccessor::new(data)?))
+    }
+
+    pub fn name(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(1)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn package(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(2)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn dependency(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(3)
+    }
+
+    pub fn public_dependency(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(10)
+    }
+
+    pub fn weak_dependency(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(11)
+    }
+
+    pub fn option_dependency(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(15)
+    }
+
+    pub fn message_type(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(4)
+    }
+
+    pub fn enum_type(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(5)
+    }
+
+    pub fn service(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(6)
+    }
+
+    pub fn extension(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(7)
+    }
+
+    pub fn syntax(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(12)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn edition(&self) -> Result<Edition> {
+        let (bytes, _) = self.0.get_value(14)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(Edition::from_i32(val as i32))
+    }
+
+    pub fn builder(buf: &mut [u8]) -> FileDescriptorProtoBuilder<'_> {
+        FileDescriptorProtoBuilder {
+            builder: ProtoBuilder::new(buf),
+        }
+    }
+}
+
+pub struct FileDescriptorProtoBuilder<'b> {
+    builder: ProtoBuilder<'b>,
+}
+
+impl<'b> FileDescriptorProtoBuilder<'b> {
+    pub fn name(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(1, value)?;
+        Ok(self)
+    }
+
+    pub fn package(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(2, value)?;
+        Ok(self)
+    }
+
+    pub fn add_dependency(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(3, value)?;
+        Ok(self)
+    }
+
+    pub fn add_public_dependency(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(10, value)?;
+        Ok(self)
+    }
+
+    pub fn add_weak_dependency(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(11, value)?;
+        Ok(self)
+    }
+
+    pub fn add_option_dependency(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(15, value)?;
+        Ok(self)
+    }
+
+    pub fn add_message_type(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(4, data)?;
+        Ok(self)
+    }
+
+    pub fn add_enum_type(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(5, data)?;
+        Ok(self)
+    }
+
+    pub fn add_service(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(6, data)?;
+        Ok(self)
+    }
+
+    pub fn add_extension(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(7, data)?;
+        Ok(self)
+    }
+
+    pub fn syntax(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(12, value)?;
+        Ok(self)
+    }
+
+    pub fn edition(mut self, value: Edition) -> Result<Self> {
+        self.builder.write_varint(14, value as u64)?;
+        Ok(self)
+    }
+
+    pub fn finish(self) -> Result<&'b mut [u8]> {
+        self.builder.finish()
+    }
+}
+
+pub struct DescriptorProto<'a>(ProtoAccessor<'a>);
+
+impl<'a> DescriptorProto<'a> {
+    pub fn new(data: &'a [u8]) -> Result<Self> {
+        Ok(Self(ProtoAccessor::new(data)?))
+    }
+
+    pub fn name(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(1)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn field(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(2)
+    }
+
+    pub fn extension(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(6)
+    }
+
+    pub fn nested_type(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(3)
+    }
+
+    pub fn enum_type(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(4)
+    }
+
+    pub fn reserved_name(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(10)
+    }
+
+    pub fn builder(buf: &mut [u8]) -> DescriptorProtoBuilder<'_> {
+        DescriptorProtoBuilder {
+            builder: ProtoBuilder::new(buf),
+        }
+    }
+}
+
+pub struct DescriptorProtoBuilder<'b> {
+    builder: ProtoBuilder<'b>,
+}
+
+impl<'b> DescriptorProtoBuilder<'b> {
+    pub fn name(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(1, value)?;
+        Ok(self)
+    }
+
+    pub fn add_field(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(2, data)?;
+        Ok(self)
+    }
+
+    pub fn add_extension(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(6, data)?;
+        Ok(self)
+    }
+
+    pub fn add_nested_type(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(3, data)?;
+        Ok(self)
+    }
+
+    pub fn add_enum_type(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(4, data)?;
+        Ok(self)
+    }
+
+    pub fn add_reserved_name(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(10, value)?;
+        Ok(self)
+    }
+
+    pub fn finish(self) -> Result<&'b mut [u8]> {
+        self.builder.finish()
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum FieldType {
+    Double = 1,
+    Float = 2,
+    Int64 = 3,
+    Uint64 = 4,
+    Int32 = 5,
+    Fixed64 = 6,
+    Fixed32 = 7,
+    Bool = 8,
+    String = 9,
+    Group = 10,
+    Message = 11,
+    Bytes = 12,
+    Uint32 = 13,
+    Enum = 14,
+    Sfixed32 = 15,
+    Sfixed64 = 16,
+    Sint32 = 17,
+    Sint64 = 18,
+}
+
+impl FieldType {
+    pub fn from_i32(value: i32) -> Self {
+        match value {
+            1 => FieldType::Double,
+            2 => FieldType::Float,
+            3 => FieldType::Int64,
+            4 => FieldType::Uint64,
+            5 => FieldType::Int32,
+            6 => FieldType::Fixed64,
+            7 => FieldType::Fixed32,
+            8 => FieldType::Bool,
+            9 => FieldType::String,
+            10 => FieldType::Group,
+            11 => FieldType::Message,
+            12 => FieldType::Bytes,
+            13 => FieldType::Uint32,
+            14 => FieldType::Enum,
+            15 => FieldType::Sfixed32,
+            16 => FieldType::Sfixed64,
+            17 => FieldType::Sint32,
+            18 => FieldType::Sint64,
+            _ => FieldType::Int32,
+        }
+    }
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum FieldLabel {
+    Optional = 1,
+    Required = 2,
+    Repeated = 3,
+}
+
+impl FieldLabel {
+    pub fn from_i32(value: i32) -> Self {
+        match value {
+            1 => FieldLabel::Optional,
+            2 => FieldLabel::Required,
+            3 => FieldLabel::Repeated,
+            _ => FieldLabel::Optional,
+        }
+    }
+}
+
+pub struct FieldDescriptorProto<'a>(ProtoAccessor<'a>);
+
+impl<'a> FieldDescriptorProto<'a> {
+    pub fn new(data: &'a [u8]) -> Result<Self> {
+        Ok(Self(ProtoAccessor::new(data)?))
+    }
+
+    pub fn name(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(1)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn number(&self) -> Result<i32> {
+        let (bytes, _) = self.0.get_value(3)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val as i32)
+    }
+
+    pub fn label(&self) -> Result<FieldLabel> {
+        let (bytes, _) = self.0.get_value(4)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(FieldLabel::from_i32(val as i32))
+    }
+
+    pub fn field_type(&self) -> Result<FieldType> {
+        let (bytes, _) = self.0.get_value(5)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(FieldType::from_i32(val as i32))
+    }
+
+    pub fn type_name(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(6)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn default_value(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(7)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn oneof_index(&self) -> Result<i32> {
+        let (bytes, _) = self.0.get_value(9)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val as i32)
+    }
+
+    pub fn json_name(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(10)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn proto3_optional(&self) -> Result<bool> {
+        let (bytes, _) = self.0.get_value(17)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val != 0)
+    }
+
+    pub fn builder(buf: &mut [u8]) -> FieldDescriptorProtoBuilder<'_> {
+        FieldDescriptorProtoBuilder {
+            builder: ProtoBuilder::new(buf),
+        }
+    }
+}
+
+pub struct FieldDescriptorProtoBuilder<'b> {
+    builder: ProtoBuilder<'b>,
+}
+
+impl<'b> FieldDescriptorProtoBuilder<'b> {
+    pub fn name(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(1, value)?;
+        Ok(self)
+    }
+
+    pub fn number(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(3, value)?;
+        Ok(self)
+    }
+
+    pub fn label(mut self, value: FieldLabel) -> Result<Self> {
+        self.builder.write_varint(4, value as u64)?;
+        Ok(self)
+    }
+
+    pub fn field_type(mut self, value: FieldType) -> Result<Self> {
+        self.builder.write_varint(5, value as u64)?;
+        Ok(self)
+    }
+
+    pub fn type_name(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(6, value)?;
+        Ok(self)
+    }
+
+    pub fn default_value(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(7, value)?;
+        Ok(self)
+    }
+
+    pub fn oneof_index(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(9, value)?;
+        Ok(self)
+    }
+
+    pub fn json_name(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(10, value)?;
+        Ok(self)
+    }
+
+    pub fn proto3_optional(mut self, value: bool) -> Result<Self> {
+        self.builder.write_varint(17, if value { 1 } else { 0 })?;
+        Ok(self)
+    }
+
+    pub fn finish(self) -> Result<&'b mut [u8]> {
+        self.builder.finish()
+    }
+}
+
+pub struct GeneratedCodeInfo<'a>(ProtoAccessor<'a>);
+
+impl<'a> GeneratedCodeInfo<'a> {
+    pub fn new(data: &'a [u8]) -> Result<Self> {
+        Ok(Self(ProtoAccessor::new(data)?))
+    }
+
+    pub fn annotation(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(1)
+    }
+
+    pub fn builder(buf: &mut [u8]) -> GeneratedCodeInfoBuilder<'_> {
+        GeneratedCodeInfoBuilder {
+            builder: ProtoBuilder::new(buf),
+        }
+    }
+}
+
+pub struct GeneratedCodeInfoBuilder<'b> {
+    builder: ProtoBuilder<'b>,
+}
+
+impl<'b> GeneratedCodeInfoBuilder<'b> {
+    pub fn add_annotation(mut self, data: &[u8]) -> Result<Self> {
+        self.builder.write_bytes(1, data)?;
+        Ok(self)
+    }
+
+    pub fn finish(self) -> Result<&'b mut [u8]> {
+        self.builder.finish()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs;
+
+    #[test]
+    fn test_read_descriptor_set() {
+        let data = include_bytes!("../../../../data/test_types.desc");
+        let set = FileDescriptorSet::new(data).expect("Failed to parse FileDescriptorSet");
+        let mut files = set.file();
+        let (file_data, _) = files.next().expect("No file descriptors found").expect("Failed to read file descriptor");
+        let file_proto = FileDescriptorProto::new(file_data).expect("Failed to parse FileDescriptorProto");
+        assert_eq!(file_proto.name().unwrap(), "data/test_types.proto");
+        assert_eq!(file_proto.package().unwrap(), "roto.test");
+    }
+}
+
+pub struct Annotation<'a>(ProtoAccessor<'a>);
+
+impl<'a> Annotation<'a> {
+    pub fn new(data: &'a [u8]) -> Result<Self> {
+        Ok(Self(ProtoAccessor::new(data)?))
+    }
+
+    pub fn path(&self) -> crate::RepeatedFieldIterator<'a> {
+        self.0.iter_repeated(1)
+    }
+
+    pub fn source_file(&self) -> Result<&'a str> {
+        let (bytes, _) = self.0.get_value(2)?;
+        str::from_utf8(bytes).map_err(|_| RotoError::WireFormatViolation)
+    }
+
+    pub fn begin(&self) -> Result<i32> {
+        let (bytes, _) = self.0.get_value(3)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val as i32)
+    }
+
+    pub fn end(&self) -> Result<i32> {
+        let (bytes, _) = self.0.get_value(4)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val as i32)
+    }
+
+    pub fn semantic(&self) -> Result<i32> {
+        let (bytes, _) = self.0.get_value(5)?;
+        let (val, _) = crate::read_varint(bytes)?;
+        Ok(val as i32)
+    }
+
+    pub fn builder(buf: &mut [u8]) -> AnnotationBuilder<'_> {
+        AnnotationBuilder {
+            builder: ProtoBuilder::new(buf),
+        }
+    }
+}
+
+pub struct AnnotationBuilder<'b> {
+    builder: ProtoBuilder<'b>,
+}
+
+impl<'b> AnnotationBuilder<'b> {
+    pub fn add_path(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(1, value)?;
+        Ok(self)
+    }
+
+    pub fn source_file(mut self, value: &str) -> Result<Self> {
+        self.builder.write_string(2, value)?;
+        Ok(self)
+    }
+
+    pub fn begin(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(3, value)?;
+        Ok(self)
+    }
+
+    pub fn end(mut self, value: i32) -> Result<Self> {
+        self.builder.write_int32(4, value)?;
+        Ok(self)
+    }
+
+    pub fn semantic(mut self, value: i32) -> Result<Self> {
+        self.builder.write_varint(5, value as u64)?;
+        Ok(self)
+    }
+
+    pub fn finish(self) -> Result<&'b mut [u8]> {
+        self.builder.finish()
+    }
+}
diff --git a/src/proto_gen/mod.rs b/src/proto_gen/mod.rs
new file mode 100644
index 0000000..b154821
--- /dev/null
+++ b/src/proto_gen/mod.rs
@@ -0,0 +1,8 @@
+pub mod google {
+    pub mod protobuf {
+        pub mod descriptor;
+        pub mod compiler {
+            pub mod plugin;
+        }
+    }
+}