fix(postgres) : int type conversion while decoding (#3173)

* fix(postgres) : int type conversion while decoding

* Check value buffer len when decoding integer type in postgres

* decode from octal for postgres i8

---------

Co-authored-by: RaghavRox <66472843+RaghavRox@users.noreply.github.com>

sqlx-postgres/src/types/int.rs

@@ -6,6 +6,31 @@ use crate::error::BoxDynError;
 use crate::types::Type;
 use crate::{PgArgumentBuffer, PgHasArrayType, PgTypeInfo, PgValueFormat, PgValueRef, Postgres};
 
+fn int_decode(value: PgValueRef<'_>) -> Result<i64, BoxDynError> {
+    Ok(match value.format() {
+        PgValueFormat::Text => value.as_str()?.parse()?,
+        PgValueFormat::Binary => {
+            let buf = value.as_bytes()?;
+
+            // Return error if buf is empty or is more than 8 bytes
+            match buf.len() {
+                0 => {
+                    return Err("Value Buffer found empty while decoding to integer type".into());
+                }
+                buf_len @ 9.. => {
+                    return Err(format!(
+                        "Value Buffer exceeds 8 bytes while decoding to integer type. Buffer size = {} bytes ", buf_len
+                    )
+                    .into());
+                }
+                _ => {}
+            }
+
+            BigEndian::read_int(buf, buf.len())
+        }
+    })
+}
+
 impl Type<Postgres> for i8 {
     fn type_info() -> PgTypeInfo {
         PgTypeInfo::CHAR
@@ -28,8 +53,26 @@ impl Encode<'_, Postgres> for i8 {
 
 impl Decode<'_, Postgres> for i8 {
     fn decode(value: PgValueRef<'_>) -> Result<Self, BoxDynError> {
-        // note: in the TEXT encoding, a value of "0" here is encoded as an empty string
-        Ok(value.as_bytes()?.get(0).copied().unwrap_or_default() as i8)
+        // note: decoding here is for the `"char"` type as Postgres does not have a native 1-byte integer type.
+        // https://github.com/postgres/postgres/blob/master/src/backend/utils/adt/char.c#L58-L60
+        match value.format() {
+            PgValueFormat::Binary => int_decode(value)?.try_into().map_err(Into::into),
+            PgValueFormat::Text => {
+                let text = value.as_str()?;
+
+                // A value of 0 is represented with the empty string.
+                if text.is_empty() {
+                    return Ok(0);
+                }
+
+                if text.starts_with('\\') {
+                    // For values between 0x80 and 0xFF, it's encoded in octal.
+                    return Ok(i8::from_str_radix(text.trim_start_matches('\\'), 8)?);
+                }
+
+                Ok(text.as_bytes()[0] as i8)
+            }
+        }
     }
 }
 
@@ -55,10 +98,7 @@ impl Encode<'_, Postgres> for i16 {
 
 impl Decode<'_, Postgres> for i16 {
     fn decode(value: PgValueRef<'_>) -> Result<Self, BoxDynError> {
-        Ok(match value.format() {
-            PgValueFormat::Binary => BigEndian::read_i16(value.as_bytes()?),
-            PgValueFormat::Text => value.as_str()?.parse()?,
-        })
+        int_decode(value)?.try_into().map_err(Into::into)
     }
 }
 
@@ -84,10 +124,7 @@ impl Encode<'_, Postgres> for i32 {
 
 impl Decode<'_, Postgres> for i32 {
     fn decode(value: PgValueRef<'_>) -> Result<Self, BoxDynError> {
-        Ok(match value.format() {
-            PgValueFormat::Binary => BigEndian::read_i32(value.as_bytes()?),
-            PgValueFormat::Text => value.as_str()?.parse()?,
-        })
+        int_decode(value)?.try_into().map_err(Into::into)
     }
 }
 
@@ -113,9 +150,6 @@ impl Encode<'_, Postgres> for i64 {
 
 impl Decode<'_, Postgres> for i64 {
     fn decode(value: PgValueRef<'_>) -> Result<Self, BoxDynError> {
-        Ok(match value.format() {
-            PgValueFormat::Binary => BigEndian::read_i64(value.as_bytes()?),
-            PgValueFormat::Text => value.as_str()?.parse()?,
-        })
+        int_decode(value)
     }
 }