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use crate::DataType; /// Used to describe a column of a [`crate::buffers::ColumnarRowSet`]. /// /// While related to to the [`crate::DataType`] of the column this is bound to, the Buffer type is /// different as it does not describe the type of the data source but the format the data is going /// to be represented in memory. While the data source is often considered to choose the buffer type /// the kind of processing which is supposed to be applied to the data may be even more important /// if choosing the a buffer for the cursor type. I.e. if you intend to print a date to standard out /// it may be more reasonable to bind it as `Text` rather than `Date`. #[derive(Clone, Copy, Debug)] pub struct BufferDescription { /// This indicates whether or not the buffer will be able to represent NULL values. This will /// cause an indicator buffer to be bound if the selected buffer kind does not already require /// one anyway. pub nullable: bool, /// The type of CData the buffer will be holding. pub kind: BufferKind, } /// This class is used together with [`crate::buffers::BufferDescription`] to specify the layout of /// buffers bound to ODBC cursors and statements. #[derive(Clone, Copy, Debug, PartialEq, Eq)] pub enum BufferKind { /// Variable sized binary buffer, holding up to `length` bytes per value. Binary { /// Maximum number of bytes per value. length: usize, }, /// Text buffer holding strings with binary length of up to `max_str_len`. Text { /// Maximum string length. Terminating zero is excluded, i.e. memory for it will be /// implicitly allocated if required. max_str_len: usize, }, /// 64 bit floating point F64, /// 32 bit floating point F32, /// Describes a buffer holding [`crate::sys::Date`] values. Date, /// Describes a buffer holding [`crate::sys::Time`] values. Time, /// Describes a buffer holding [`crate::sys::Timestamp`] values. Timestamp, /// Signed 8 Bit integer I8, /// Signed 16 Bit integer I16, /// Signed 32 Bit integer I32, /// Signed 64 Bit integer I64, /// Unsigned 8 Bit integer U8, /// Can either be zero or one Bit, } impl BufferKind { /// Describe a buffer which fits best the SQL Data Type. /// /// ``` /// use odbc_api::{DataType, buffers::BufferKind}; /// /// assert_eq!(BufferKind::from_data_type(DataType::Unknown), None); /// assert_eq!( /// BufferKind::from_data_type(DataType::Numeric { precision: 2, scale: 0 }), /// Some(BufferKind::I8) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Numeric { precision: 9, scale: 0 }), /// Some(BufferKind::I32) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Numeric { precision: 18, scale: 0 }), /// Some(BufferKind::I64) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Numeric { precision: 20, scale: 5 }), /// Some(BufferKind::Text { max_str_len: 20 + 2 }) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Varchar { length: 42 }), /// Some(BufferKind::Text { max_str_len: 42 }) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::BigInt), /// Some(BufferKind::I64) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Integer), /// Some(BufferKind::I32) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::SmallInt), /// Some(BufferKind::I16) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::TinyInt), /// Some(BufferKind::I8) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Float), /// Some(BufferKind::F32) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Double), /// Some(BufferKind::F64) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Date), /// Some(BufferKind::Date) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Time { precision: 0 }), /// Some(BufferKind::Time) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Bit), /// Some(BufferKind::Bit) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Time { precision: 3 }), /// Some(BufferKind::Text { max_str_len: 12 }) /// ); /// assert_eq!( /// BufferKind::from_data_type(DataType::Timestamp { precision: 3 }), /// Some(BufferKind::Timestamp) /// ); /// ``` pub fn from_data_type(data_type: DataType) -> Option<Self> { let buffer_kind = match data_type { DataType::Unknown | DataType::Other { data_type: _, column_size: _, decimal_digits: _ } => return None, DataType::Numeric { precision, scale } | DataType::Decimal { precision, scale } if scale == 0 && precision < 3 => BufferKind::I8, DataType::Numeric { precision, scale } | DataType::Decimal { precision, scale } if scale == 0 && precision < 10 => BufferKind::I32, DataType::Numeric { precision, scale } | DataType::Decimal { precision, scale } if scale == 0 && precision < 19 => BufferKind::I64, DataType::Integer => BufferKind::I32, DataType::SmallInt => BufferKind::I16, DataType::Float | DataType::Real => BufferKind::F32, DataType::Double => BufferKind::F64, DataType::Date => BufferKind::Date, DataType::Time { precision: 0 } => BufferKind::Time, DataType::Timestamp { precision: _ } => BufferKind::Timestamp, DataType::BigInt => BufferKind::I64, DataType::TinyInt => BufferKind::I8, DataType::Bit => BufferKind::Bit, DataType::Varbinary { length } | DataType::Binary { length } => BufferKind::Binary { length }, DataType::Varchar { length } | DataType::WVarchar { length } // Currently no special buffers for fixed lengths text implemented. | DataType::Char { length } => BufferKind::Text { max_str_len : length }, // Specialized buffers for Numeric and decimal are not yet supported. | DataType::Numeric { precision: _, scale: _ } | DataType::Decimal { precision: _, scale: _ } | DataType::Time { precision: _ } => BufferKind::Text { max_str_len: data_type.display_size().unwrap() }, }; Some(buffer_kind) } }