From 647f67266f35bac85ca6ac506447330d1c71e7fb Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 27 May 2023 18:06:52 -0300
Subject: [PATCH 01/25] =?UTF-8?q?[desafio-07]=20Primeira=20implementa?=
 =?UTF-8?q?=C3=A7=C3=A3o?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 desafio-07/MatMercer/go/tac.go | 70 ++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 desafio-07/MatMercer/go/tac.go

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
new file mode 100644
index 000000000..131e76d49
--- /dev/null
+++ b/desafio-07/MatMercer/go/tac.go
@@ -0,0 +1,70 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"os"
+)
+
+const bufSize = int64(32)
+
+func check(e error) {
+	if e != nil {
+		errAndExit(fmt.Sprintf("tac error: %v", e))
+	}
+}
+
+func errAndExit(msg string) {
+	os.Stderr.WriteString(msg + "\n")
+	os.Exit(1)
+}
+
+func main() {
+	args := os.Args[1:]
+
+	if len(args) != 1 {
+		errAndExit("usage: tac [file]")
+	}
+
+	fileName := args[0]
+
+	f, err := os.Open(fileName)
+	check(err)
+	defer f.Close()
+	fi, err := f.Stat()
+	check(err)
+
+	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
+	out := os.Stdout
+	b := make([]byte, bufSize)
+	end := fi.Size()
+	maxReadIdx := bufSize - 1
+	start := end
+	for start != 0 {
+		start -= bufSize
+		if start < 0 {
+			// prevent over reading if result is less than buf size
+			maxReadIdx += start
+			start = 0
+		}
+
+		_, err = f.Seek(start, io.SeekStart)
+		check(err)
+		_, err = f.Read(b[:maxReadIdx])
+		check(err)
+
+		// search until backwards \n and prints it
+		lastEnd := maxReadIdx
+		for i := maxReadIdx; i >= 0; i-- {
+			if b[i] == '\n' {
+				_, err = out.Write(b[i+1 : lastEnd])
+				check(err)
+			}
+
+			if i == 0 {
+				_, err = out.Write(b[i:lastEnd])
+				check(err)
+			}
+		}
+	}
+}

From b282aeb779555bf8fa7f959b535dbc8c2832136f Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 27 May 2023 18:35:33 -0300
Subject: [PATCH 02/25] [desafio-07] Arruma buffer pequeno dando erro

---
 desafio-07/MatMercer/go/tac.go | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 131e76d49..409357a11 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"fmt"
 	"io"
 	"os"
@@ -38,33 +39,50 @@ func main() {
 	out := os.Stdout
 	b := make([]byte, bufSize)
 	end := fi.Size()
-	maxReadIdx := bufSize - 1
+	maxRead := bufSize
 	start := end
+	acc := bytes.NewBuffer([]byte{})
 	for start != 0 {
 		start -= bufSize
 		if start < 0 {
 			// prevent over reading if result is less than buf size
-			maxReadIdx += start
+			maxRead += start
 			start = 0
 		}
 
 		_, err = f.Seek(start, io.SeekStart)
 		check(err)
-		_, err = f.Read(b[:maxReadIdx])
+		_, err = f.Read(b[:maxRead])
 		check(err)
 
 		// search until backwards \n and prints it
-		lastEnd := maxReadIdx
-		for i := maxReadIdx; i >= 0; i-- {
+		lastEnd := maxRead
+		for i := maxRead - 1; i >= 0; i-- {
 			if b[i] == '\n' {
 				_, err = out.Write(b[i+1 : lastEnd])
 				check(err)
+				_, err = out.Write(acc.Bytes())
+				check(err)
+				_, err = out.Write([]byte{'\n'})
+				check(err)
+				acc.Reset()
+				lastEnd = i
 			}
 
 			if i == 0 {
-				_, err = out.Write(b[i:lastEnd])
+				newAcc := bytes.NewBuffer([]byte{})
+				_, err = newAcc.Write(b[i:lastEnd])
 				check(err)
+				_, err = newAcc.Write(acc.Bytes())
+				check(err)
+				acc.Reset()
+				acc = newAcc
 			}
 		}
+		if start == 0 {
+			_, err = out.Write(acc.Bytes())
+			check(err)
+			acc.Reset()
+		}
 	}
 }

From 3df68ab0d0da29ceb0842967627c3aa80bfa270a Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 27 May 2023 18:46:59 -0300
Subject: [PATCH 03/25] [desafio-07] Code cleanup

---
 desafio-07/MatMercer/go/tac.go | 39 +++++++++++++++++-----------------
 1 file changed, 20 insertions(+), 19 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 409357a11..cadc841ed 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -35,13 +35,11 @@ func main() {
 	fi, err := f.Stat()
 	check(err)
 
-	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
-	out := os.Stdout
 	b := make([]byte, bufSize)
 	end := fi.Size()
 	maxRead := bufSize
 	start := end
-	acc := bytes.NewBuffer([]byte{})
+	lineAcc := bytes.NewBuffer([]byte{})
 	for start != 0 {
 		start -= bufSize
 		if start < 0 {
@@ -59,30 +57,33 @@ func main() {
 		lastEnd := maxRead
 		for i := maxRead - 1; i >= 0; i-- {
 			if b[i] == '\n' {
-				_, err = out.Write(b[i+1 : lastEnd])
-				check(err)
-				_, err = out.Write(acc.Bytes())
-				check(err)
-				_, err = out.Write([]byte{'\n'})
-				check(err)
-				acc.Reset()
-				lastEnd = i
+				// write everything but '\n', since b[i] == '\n'
+				out(b[i+1 : lastEnd])
+				// need to write accumulated value
+				out(lineAcc.Bytes())
+				lineAcc.Reset()
+				// +1 here makes '\n' be printed in next iteration
+				lastEnd = i + 1
 			}
 
 			if i == 0 {
 				newAcc := bytes.NewBuffer([]byte{})
 				_, err = newAcc.Write(b[i:lastEnd])
 				check(err)
-				_, err = newAcc.Write(acc.Bytes())
+				_, err = newAcc.Write(lineAcc.Bytes())
 				check(err)
-				acc.Reset()
-				acc = newAcc
+				lineAcc.Reset()
+				lineAcc = newAcc
 			}
 		}
-		if start == 0 {
-			_, err = out.Write(acc.Bytes())
-			check(err)
-			acc.Reset()
-		}
 	}
+	// prints last chunk of data
+	out(lineAcc.Bytes())
+}
+
+// out outputs to os.Stdout checking for errors
+func out(b []byte) {
+	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
+	_, err := os.Stdout.Write(b)
+	check(err)
 }

From 9a1058fdc06e30d99afa89e08851b0f2e0f930a1 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 27 May 2023 20:51:23 -0300
Subject: [PATCH 04/25] =?UTF-8?q?[desafio-07]=20Melhora=20performance=20co?=
 =?UTF-8?q?m=20arquivos=20pequenos=20e=20limpa=20c=C3=B3digo?=
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

---
 desafio-07/MatMercer/go/tac.go | 27 +++++++++++++++++++--------
 1 file changed, 19 insertions(+), 8 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index cadc841ed..65eeda373 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -7,7 +7,12 @@ import (
 	"os"
 )
 
-const bufSize = int64(32)
+func main() {
+	tac()
+}
+
+// in MB size, currently the program uses a max of 2*bufSize iff file size > bufSize
+const maxBufSize = int64(250 << (10 * 2))
 
 func check(e error) {
 	if e != nil {
@@ -16,11 +21,11 @@ func check(e error) {
 }
 
 func errAndExit(msg string) {
-	os.Stderr.WriteString(msg + "\n")
+	_, _ = os.Stderr.WriteString(msg + "\n")
 	os.Exit(1)
 }
 
-func main() {
+func tac() {
 	args := os.Args[1:]
 
 	if len(args) != 1 {
@@ -35,10 +40,11 @@ func main() {
 	fi, err := f.Stat()
 	check(err)
 
+	fs := fi.Size()
+	bufSize := min(fs, maxBufSize)
 	b := make([]byte, bufSize)
-	end := fi.Size()
 	maxRead := bufSize
-	start := end
+	start := fs
 	lineAcc := bytes.NewBuffer([]byte{})
 	for start != 0 {
 		start -= bufSize
@@ -67,9 +73,7 @@ func main() {
 			}
 
 			if i == 0 {
-				newAcc := bytes.NewBuffer([]byte{})
-				_, err = newAcc.Write(b[i:lastEnd])
-				check(err)
+				newAcc := bytes.NewBuffer(b[i:lastEnd])
 				_, err = newAcc.Write(lineAcc.Bytes())
 				check(err)
 				lineAcc.Reset()
@@ -87,3 +91,10 @@ func out(b []byte) {
 	_, err := os.Stdout.Write(b)
 	check(err)
 }
+
+func min(x int64, y int64) int64 {
+	if x > y {
+		return y
+	}
+	return x
+}

From d46824ccbd92b83f91111e138fd5e9347598dc49 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sun, 28 May 2023 15:41:05 -0300
Subject: [PATCH 05/25] [desafio-07] Add reverse reader

---
 desafio-07/MatMercer/go/tac.go | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 65eeda373..a1bb5533a 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -46,6 +46,7 @@ func tac() {
 	maxRead := bufSize
 	start := fs
 	lineAcc := bytes.NewBuffer([]byte{})
+	r := NewReverseReader(f, fs)
 	for start != 0 {
 		start -= bufSize
 		if start < 0 {
@@ -54,9 +55,7 @@ func tac() {
 			start = 0
 		}
 
-		_, err = f.Seek(start, io.SeekStart)
-		check(err)
-		_, err = f.Read(b[:maxRead])
+		_, err = r.Read(b[:maxRead])
 		check(err)
 
 		// search until backwards \n and prints it
@@ -98,3 +97,28 @@ func min(x int64, y int64) int64 {
 	}
 	return x
 }
+
+type ReverseReader struct {
+	f      *os.File
+	offset int64
+}
+
+func NewReverseReader(f *os.File, size int64) *ReverseReader {
+	return &ReverseReader{
+		f,
+		size,
+	}
+}
+
+func (r *ReverseReader) Read(b []byte) (n int, err error) {
+	r.offset -= int64(len(b))
+	_, err = r.f.Seek(r.offset, io.SeekStart)
+	if err != nil {
+		return 0, err
+	}
+	read, err := r.f.Read(b)
+	if err != nil {
+		return 0, err
+	}
+	return read, nil
+}

From bcb27f5e9d258c93f54b7d91c818b10348a3b273 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sun, 28 May 2023 16:30:20 -0300
Subject: [PATCH 06/25] [desafio-07] Corrige problema de ultimo output

---
 desafio-07/MatMercer/go/tac.go | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index a1bb5533a..564b87a93 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -72,7 +72,9 @@ func tac() {
 			}
 
 			if i == 0 {
-				newAcc := bytes.NewBuffer(b[i:lastEnd])
+				newAcc := bytes.NewBuffer(nil)
+				_, err = newAcc.Write(b[i:lastEnd])
+				check(err)
 				_, err = newAcc.Write(lineAcc.Bytes())
 				check(err)
 				lineAcc.Reset()

From 8e1104a6e30c7ea418d36c52b154c9e5b2d5b978 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sun, 28 May 2023 16:37:14 -0300
Subject: [PATCH 07/25] [desafio-07] Melhora performance bufferizando stdout

---
 desafio-07/MatMercer/go/tac.go | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 564b87a93..5a8535633 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bufio"
 	"bytes"
 	"fmt"
 	"io"
@@ -14,6 +15,8 @@ func main() {
 // in MB size, currently the program uses a max of 2*bufSize iff file size > bufSize
 const maxBufSize = int64(250 << (10 * 2))
 
+var stdout *bufio.Writer
+
 func check(e error) {
 	if e != nil {
 		errAndExit(fmt.Sprintf("tac error: %v", e))
@@ -40,6 +43,10 @@ func tac() {
 	fi, err := f.Stat()
 	check(err)
 
+	// buffers stdout by 128kb
+	stdout = bufio.NewWriterSize(os.Stdout, 128<<(10))
+	defer stdout.Flush()
+
 	fs := fi.Size()
 	bufSize := min(fs, maxBufSize)
 	b := make([]byte, bufSize)
@@ -89,7 +96,7 @@ func tac() {
 // out outputs to os.Stdout checking for errors
 func out(b []byte) {
 	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
-	_, err := os.Stdout.Write(b)
+	_, err := stdout.Write(b)
 	check(err)
 }
 

From a58271cb9d67617a15f01063bdf59d2a55899233 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sun, 28 May 2023 16:45:03 -0300
Subject: [PATCH 08/25] [desafio-07] Tuning

---
 desafio-07/MatMercer/go/tac.go | 1 -
 1 file changed, 1 deletion(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 5a8535633..bd152b2c8 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -84,7 +84,6 @@ func tac() {
 				check(err)
 				_, err = newAcc.Write(lineAcc.Bytes())
 				check(err)
-				lineAcc.Reset()
 				lineAcc = newAcc
 			}
 		}

From 84e111910230510aa3f43fca26e9c1a7c91d1f2b Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sun, 28 May 2023 16:49:08 -0300
Subject: [PATCH 09/25] [desafio-07] Readme

---
 desafio-07/MatMercer/go/README.md | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)
 create mode 100644 desafio-07/MatMercer/go/README.md

diff --git a/desafio-07/MatMercer/go/README.md b/desafio-07/MatMercer/go/README.md
new file mode 100644
index 000000000..ae71a4f39
--- /dev/null
+++ b/desafio-07/MatMercer/go/README.md
@@ -0,0 +1,30 @@
+# Solução desafio 7 unix tac em Go
+
+Executar:
+
+```bash
+go build tac.go
+./tac 1GB.txt > out.txt
+md5sum out.txt
+2b4fd25f11d75c285ec69ecac420bd07  out.txt
+```
+
+Para testar os 512MB de memória com control groups v1:
+
+```bash
+# setup cgroup
+export CGROUP=osProgramadoresD7
+export CGROUPP="memory/$CGROUP"
+sudo cgcreate -t $USER:$USER -a $USER:$USER -g memory:"$CGROUP"
+echo 512M > "/sys/fs/cgroup/$CGROUPP/memory.limit_in_bytes"
+echo 0 > "/sys/fs/cgroup/$CGROUPP/memory.swappiness"
+
+# run in cgroup
+cgexec -g memory:osProgramadoresD7 ./tac 1GB.txt > out.txt
+md5sum out.txt
+2b4fd25f11d75c285ec69ecac420bd07  out.txt
+
+# check max mem used
+cat "/sys/fs/cgroup/$CGROUPP/memory.max_usage_in_bytes" | numfmt --to=iec
+512M
+```

From afa6ca68bb891597b6cd0b9f9ee0388983c596c4 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 14:56:51 -0300
Subject: [PATCH 10/25] [desafio-07] Main final arquivo

---
 desafio-07/MatMercer/go/tac.go | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index bd152b2c8..daf0c460d 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -8,10 +8,6 @@ import (
 	"os"
 )
 
-func main() {
-	tac()
-}
-
 // in MB size, currently the program uses a max of 2*bufSize iff file size > bufSize
 const maxBufSize = int64(250 << (10 * 2))
 
@@ -130,3 +126,7 @@ func (r *ReverseReader) Read(b []byte) (n int, err error) {
 	}
 	return read, nil
 }
+
+func main() {
+	tac()
+}

From 21026571c9afe7a6dec5b12e5a83c40c000b27f1 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 14:57:51 -0300
Subject: [PATCH 11/25] [desafio-07] args -> os.Args

---
 desafio-07/MatMercer/go/tac.go | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index daf0c460d..2f3a56353 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -25,14 +25,11 @@ func errAndExit(msg string) {
 }
 
 func tac() {
-	args := os.Args[1:]
-
-	if len(args) != 1 {
+	if len(os.Args) != 2 {
 		errAndExit("usage: tac [file]")
 	}
 
-	fileName := args[0]
-
+	fileName := os.Args[0]
 	f, err := os.Open(fileName)
 	check(err)
 	defer f.Close()

From 6088fc671842aca29258e766d5af10ff9efdef6e Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 14:59:13 -0300
Subject: [PATCH 12/25] [desafio-07] Use log.fatalX

---
 desafio-07/MatMercer/go/tac.go | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 2f3a56353..0de59b92e 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -3,8 +3,8 @@ package main
 import (
 	"bufio"
 	"bytes"
-	"fmt"
 	"io"
+	"log"
 	"os"
 )
 
@@ -15,18 +15,13 @@ var stdout *bufio.Writer
 
 func check(e error) {
 	if e != nil {
-		errAndExit(fmt.Sprintf("tac error: %v", e))
+		log.Fatalf("tac error: %v", e)
 	}
 }
 
-func errAndExit(msg string) {
-	_, _ = os.Stderr.WriteString(msg + "\n")
-	os.Exit(1)
-}
-
 func tac() {
 	if len(os.Args) != 2 {
-		errAndExit("usage: tac [file]")
+		log.Fatalln("usage: tac [file]")
 	}
 
 	fileName := os.Args[0]

From 1221b984845ff0d026c9af96b15359903ee866f7 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:04:46 -0300
Subject: [PATCH 13/25] [desafio-07] Remove check()

---
 desafio-07/MatMercer/go/tac.go | 106 ++++++++++++++++++---------------
 1 file changed, 57 insertions(+), 49 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 0de59b92e..a9c4aba4e 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -19,17 +19,62 @@ func check(e error) {
 	}
 }
 
-func tac() {
+// out outputs to os.Stdout checking for errors
+func out(b []byte) {
+	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
+	_, err := stdout.Write(b)
+	if err != nil {
+		log.Fatalf("tac error: %v", err)
+	}
+}
+
+func min(x int64, y int64) int64 {
+	if x > y {
+		return y
+	}
+	return x
+}
+
+type ReverseReader struct {
+	f      *os.File
+	offset int64
+}
+
+func NewReverseReader(f *os.File, size int64) *ReverseReader {
+	return &ReverseReader{
+		f,
+		size,
+	}
+}
+
+func (r *ReverseReader) Read(b []byte) (n int, err error) {
+	r.offset -= int64(len(b))
+	_, err = r.f.Seek(r.offset, io.SeekStart)
+	if err != nil {
+		return 0, err
+	}
+	read, err := r.f.Read(b)
+	if err != nil {
+		return 0, err
+	}
+	return read, nil
+}
+
+func main() {
 	if len(os.Args) != 2 {
 		log.Fatalln("usage: tac [file]")
 	}
 
 	fileName := os.Args[0]
 	f, err := os.Open(fileName)
-	check(err)
+	if err != nil {
+		log.Fatalf("tac error: %v", err)
+	}
 	defer f.Close()
 	fi, err := f.Stat()
-	check(err)
+	if err != nil {
+		log.Fatalf("tac error: %v", err)
+	}
 
 	// buffers stdout by 128kb
 	stdout = bufio.NewWriterSize(os.Stdout, 128<<(10))
@@ -51,7 +96,9 @@ func tac() {
 		}
 
 		_, err = r.Read(b[:maxRead])
-		check(err)
+		if err != nil {
+			log.Fatalf("tac error: %v", err)
+		}
 
 		// search until backwards \n and prints it
 		lastEnd := maxRead
@@ -69,9 +116,13 @@ func tac() {
 			if i == 0 {
 				newAcc := bytes.NewBuffer(nil)
 				_, err = newAcc.Write(b[i:lastEnd])
-				check(err)
+				if err != nil {
+					log.Fatalf("tac error: %v", err)
+				}
 				_, err = newAcc.Write(lineAcc.Bytes())
-				check(err)
+				if err != nil {
+					log.Fatalf("tac error: %v", err)
+				}
 				lineAcc = newAcc
 			}
 		}
@@ -79,46 +130,3 @@ func tac() {
 	// prints last chunk of data
 	out(lineAcc.Bytes())
 }
-
-// out outputs to os.Stdout checking for errors
-func out(b []byte) {
-	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
-	_, err := stdout.Write(b)
-	check(err)
-}
-
-func min(x int64, y int64) int64 {
-	if x > y {
-		return y
-	}
-	return x
-}
-
-type ReverseReader struct {
-	f      *os.File
-	offset int64
-}
-
-func NewReverseReader(f *os.File, size int64) *ReverseReader {
-	return &ReverseReader{
-		f,
-		size,
-	}
-}
-
-func (r *ReverseReader) Read(b []byte) (n int, err error) {
-	r.offset -= int64(len(b))
-	_, err = r.f.Seek(r.offset, io.SeekStart)
-	if err != nil {
-		return 0, err
-	}
-	read, err := r.f.Read(b)
-	if err != nil {
-		return 0, err
-	}
-	return read, nil
-}
-
-func main() {
-	tac()
-}

From 1c7628f7d0b95da17810d37ccb28b0fbd34c3a6e Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:08:55 -0300
Subject: [PATCH 14/25] [desafio-07] Remove out()

---
 desafio-07/MatMercer/go/tac.go | 27 +++++++++++++++------------
 1 file changed, 15 insertions(+), 12 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index a9c4aba4e..49e75773e 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -19,15 +19,6 @@ func check(e error) {
 	}
 }
 
-// out outputs to os.Stdout checking for errors
-func out(b []byte) {
-	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
-	_, err := stdout.Write(b)
-	if err != nil {
-		log.Fatalf("tac error: %v", err)
-	}
-}
-
 func min(x int64, y int64) int64 {
 	if x > y {
 		return y
@@ -105,9 +96,17 @@ func main() {
 		for i := maxRead - 1; i >= 0; i-- {
 			if b[i] == '\n' {
 				// write everything but '\n', since b[i] == '\n'
-				out(b[i+1 : lastEnd])
+				// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
+				_, err = stdout.Write(b[i+1 : lastEnd])
+				if err != nil {
+					log.Fatalf("tac error: %v", err)
+				}
 				// need to write accumulated value
-				out(lineAcc.Bytes())
+				// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
+				_, err = stdout.Write(lineAcc.Bytes())
+				if err != nil {
+					log.Fatalf("tac error: %v", err)
+				}
 				lineAcc.Reset()
 				// +1 here makes '\n' be printed in next iteration
 				lastEnd = i + 1
@@ -128,5 +127,9 @@ func main() {
 		}
 	}
 	// prints last chunk of data
-	out(lineAcc.Bytes())
+	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
+	_, err = stdout.Write(lineAcc.Bytes())
+	if err != nil {
+		log.Fatalf("tac error: %v", err)
+	}
 }

From 8b9faa3893669c932b35d97ffff79adfc3adcc90 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:09:50 -0300
Subject: [PATCH 15/25] [desafio-07] Manual flush

---
 desafio-07/MatMercer/go/tac.go | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 49e75773e..931b8ae08 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -69,7 +69,6 @@ func main() {
 
 	// buffers stdout by 128kb
 	stdout = bufio.NewWriterSize(os.Stdout, 128<<(10))
-	defer stdout.Flush()
 
 	fs := fi.Size()
 	bufSize := min(fs, maxBufSize)
@@ -132,4 +131,9 @@ func main() {
 	if err != nil {
 		log.Fatalf("tac error: %v", err)
 	}
+
+	err = stdout.Flush()
+	if err != nil {
+		log.Fatalf("tac error: %v", err)
+	}
 }

From a96d742ce4d4ca2f7bd0ab0d45bbe559ab12c511 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:25:58 -0300
Subject: [PATCH 16/25] [desafio-07] Fix filename bug

---
 desafio-07/MatMercer/go/tac.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 931b8ae08..432120e85 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -56,7 +56,7 @@ func main() {
 		log.Fatalln("usage: tac [file]")
 	}
 
-	fileName := os.Args[0]
+	fileName := os.Args[1]
 	f, err := os.Open(fileName)
 	if err != nil {
 		log.Fatalf("tac error: %v", err)

From 75953502ecccfd7af84d06c3d4a982dce923a5e2 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:33:58 -0300
Subject: [PATCH 17/25] [desafio-07] Unbuf tac

---
 desafio-07/MatMercer/go/tac.go | 30 ++++--------------------------
 1 file changed, 4 insertions(+), 26 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 432120e85..8f09ea195 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -1,8 +1,8 @@
 package main
 
 import (
-	"bufio"
 	"bytes"
+	"fmt"
 	"io"
 	"log"
 	"os"
@@ -11,8 +11,6 @@ import (
 // in MB size, currently the program uses a max of 2*bufSize iff file size > bufSize
 const maxBufSize = int64(250 << (10 * 2))
 
-var stdout *bufio.Writer
-
 func check(e error) {
 	if e != nil {
 		log.Fatalf("tac error: %v", e)
@@ -67,9 +65,6 @@ func main() {
 		log.Fatalf("tac error: %v", err)
 	}
 
-	// buffers stdout by 128kb
-	stdout = bufio.NewWriterSize(os.Stdout, 128<<(10))
-
 	fs := fi.Size()
 	bufSize := min(fs, maxBufSize)
 	b := make([]byte, bufSize)
@@ -95,17 +90,9 @@ func main() {
 		for i := maxRead - 1; i >= 0; i-- {
 			if b[i] == '\n' {
 				// write everything but '\n', since b[i] == '\n'
-				// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
-				_, err = stdout.Write(b[i+1 : lastEnd])
-				if err != nil {
-					log.Fatalf("tac error: %v", err)
-				}
+				fmt.Print(string(b[i+1 : lastEnd]))
 				// need to write accumulated value
-				// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
-				_, err = stdout.Write(lineAcc.Bytes())
-				if err != nil {
-					log.Fatalf("tac error: %v", err)
-				}
+				fmt.Print(lineAcc.String())
 				lineAcc.Reset()
 				// +1 here makes '\n' be printed in next iteration
 				lastEnd = i + 1
@@ -126,14 +113,5 @@ func main() {
 		}
 	}
 	// prints last chunk of data
-	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
-	_, err = stdout.Write(lineAcc.Bytes())
-	if err != nil {
-		log.Fatalf("tac error: %v", err)
-	}
-
-	err = stdout.Flush()
-	if err != nil {
-		log.Fatalf("tac error: %v", err)
-	}
+	fmt.Print(lineAcc)
 }

From 5eb4085418f772104c37c3ffe2e659d9ded7b36d Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:35:12 -0300
Subject: [PATCH 18/25] Revert "[desafio-07] Unbuf tac"

This reverts commit 75953502ecccfd7af84d06c3d4a982dce923a5e2.
---
 desafio-07/MatMercer/go/tac.go | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 8f09ea195..432120e85 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -1,8 +1,8 @@
 package main
 
 import (
+	"bufio"
 	"bytes"
-	"fmt"
 	"io"
 	"log"
 	"os"
@@ -11,6 +11,8 @@ import (
 // in MB size, currently the program uses a max of 2*bufSize iff file size > bufSize
 const maxBufSize = int64(250 << (10 * 2))
 
+var stdout *bufio.Writer
+
 func check(e error) {
 	if e != nil {
 		log.Fatalf("tac error: %v", e)
@@ -65,6 +67,9 @@ func main() {
 		log.Fatalf("tac error: %v", err)
 	}
 
+	// buffers stdout by 128kb
+	stdout = bufio.NewWriterSize(os.Stdout, 128<<(10))
+
 	fs := fi.Size()
 	bufSize := min(fs, maxBufSize)
 	b := make([]byte, bufSize)
@@ -90,9 +95,17 @@ func main() {
 		for i := maxRead - 1; i >= 0; i-- {
 			if b[i] == '\n' {
 				// write everything but '\n', since b[i] == '\n'
-				fmt.Print(string(b[i+1 : lastEnd]))
+				// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
+				_, err = stdout.Write(b[i+1 : lastEnd])
+				if err != nil {
+					log.Fatalf("tac error: %v", err)
+				}
 				// need to write accumulated value
-				fmt.Print(lineAcc.String())
+				// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
+				_, err = stdout.Write(lineAcc.Bytes())
+				if err != nil {
+					log.Fatalf("tac error: %v", err)
+				}
 				lineAcc.Reset()
 				// +1 here makes '\n' be printed in next iteration
 				lastEnd = i + 1
@@ -113,5 +126,14 @@ func main() {
 		}
 	}
 	// prints last chunk of data
-	fmt.Print(lineAcc)
+	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
+	_, err = stdout.Write(lineAcc.Bytes())
+	if err != nil {
+		log.Fatalf("tac error: %v", err)
+	}
+
+	err = stdout.Flush()
+	if err != nil {
+		log.Fatalf("tac error: %v", err)
+	}
 }

From 14e334be6b4247ba94be2e1269db2c3e4a7bbb9f Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:44:50 -0300
Subject: [PATCH 19/25] [desafio-07] Cleanup

---
 desafio-07/MatMercer/go/tac.go | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 432120e85..b5f8b0605 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -13,12 +13,6 @@ const maxBufSize = int64(250 << (10 * 2))
 
 var stdout *bufio.Writer
 
-func check(e error) {
-	if e != nil {
-		log.Fatalf("tac error: %v", e)
-	}
-}
-
 func min(x int64, y int64) int64 {
 	if x > y {
 		return y
@@ -61,7 +55,6 @@ func main() {
 	if err != nil {
 		log.Fatalf("tac error: %v", err)
 	}
-	defer f.Close()
 	fi, err := f.Stat()
 	if err != nil {
 		log.Fatalf("tac error: %v", err)
@@ -95,22 +88,22 @@ func main() {
 		for i := maxRead - 1; i >= 0; i-- {
 			if b[i] == '\n' {
 				// write everything but '\n', since b[i] == '\n'
-				// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
 				_, err = stdout.Write(b[i+1 : lastEnd])
 				if err != nil {
 					log.Fatalf("tac error: %v", err)
 				}
-				// need to write accumulated value
-				// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
+				// writes accumulated value
 				_, err = stdout.Write(lineAcc.Bytes())
 				if err != nil {
 					log.Fatalf("tac error: %v", err)
 				}
+				// reset the accumulator to receive next line
 				lineAcc.Reset()
-				// +1 here makes '\n' be printed in next iteration
+				// makes '\n' be printed in next iteration
 				lastEnd = i + 1
 			}
 
+			// on last iteration, create a new accumulator with [max-read][current-accumulator]
 			if i == 0 {
 				newAcc := bytes.NewBuffer(nil)
 				_, err = newAcc.Write(b[i:lastEnd])
@@ -125,6 +118,9 @@ func main() {
 			}
 		}
 	}
+	// closes the file
+	_ = f.Close()
+
 	// prints last chunk of data
 	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
 	_, err = stdout.Write(lineAcc.Bytes())

From 1fa573e46ad7c0013d26a2005dd5ef7c73d366b6 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:50:06 -0300
Subject: [PATCH 20/25] [desafio-07] Stderr logger

---
 desafio-07/MatMercer/go/tac.go | 41 +++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 15 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index b5f8b0605..b8452f1ad 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -13,6 +13,7 @@ const maxBufSize = int64(250 << (10 * 2))
 
 var stdout *bufio.Writer
 
+// min standard math.Min supports only float64
 func min(x int64, y int64) int64 {
 	if x > y {
 		return y
@@ -45,19 +46,14 @@ func (r *ReverseReader) Read(b []byte) (n int, err error) {
 	return read, nil
 }
 
-func main() {
-	if len(os.Args) != 2 {
-		log.Fatalln("usage: tac [file]")
-	}
-
-	fileName := os.Args[1]
+func tac(fileName string) error {
 	f, err := os.Open(fileName)
 	if err != nil {
-		log.Fatalf("tac error: %v", err)
+		return err
 	}
 	fi, err := f.Stat()
 	if err != nil {
-		log.Fatalf("tac error: %v", err)
+		return err
 	}
 
 	// buffers stdout by 128kb
@@ -80,7 +76,7 @@ func main() {
 
 		_, err = r.Read(b[:maxRead])
 		if err != nil {
-			log.Fatalf("tac error: %v", err)
+			return err
 		}
 
 		// search until backwards \n and prints it
@@ -90,12 +86,12 @@ func main() {
 				// write everything but '\n', since b[i] == '\n'
 				_, err = stdout.Write(b[i+1 : lastEnd])
 				if err != nil {
-					log.Fatalf("tac error: %v", err)
+					return err
 				}
 				// writes accumulated value
 				_, err = stdout.Write(lineAcc.Bytes())
 				if err != nil {
-					log.Fatalf("tac error: %v", err)
+					return err
 				}
 				// reset the accumulator to receive next line
 				lineAcc.Reset()
@@ -108,11 +104,11 @@ func main() {
 				newAcc := bytes.NewBuffer(nil)
 				_, err = newAcc.Write(b[i:lastEnd])
 				if err != nil {
-					log.Fatalf("tac error: %v", err)
+					return err
 				}
 				_, err = newAcc.Write(lineAcc.Bytes())
 				if err != nil {
-					log.Fatalf("tac error: %v", err)
+					return err
 				}
 				lineAcc = newAcc
 			}
@@ -125,11 +121,26 @@ func main() {
 	// fmt.Println is unbuffered https://github.com/golang/go/issues/36619
 	_, err = stdout.Write(lineAcc.Bytes())
 	if err != nil {
-		log.Fatalf("tac error: %v", err)
+		return err
 	}
 
 	err = stdout.Flush()
 	if err != nil {
-		log.Fatalf("tac error: %v", err)
+		return err
+	}
+
+	return nil
+}
+
+func main() {
+	logger := log.New(os.Stderr, "", 0)
+	if len(os.Args) != 2 {
+		logger.Fatalln("usage: tac [file]")
+	}
+
+	fileName := os.Args[1]
+	err := tac(fileName)
+	if err != nil {
+		logger.Fatalf("tac error: %v", err)
 	}
 }

From 41277925923c96fd10f17998cb50980444d4e1b8 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:50:52 -0300
Subject: [PATCH 21/25] [desafio-07] *ReverseReader -> ReverseReader

---
 desafio-07/MatMercer/go/tac.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index b8452f1ad..2970c3f63 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -33,7 +33,7 @@ func NewReverseReader(f *os.File, size int64) *ReverseReader {
 	}
 }
 
-func (r *ReverseReader) Read(b []byte) (n int, err error) {
+func (r ReverseReader) Read(b []byte) (n int, err error) {
 	r.offset -= int64(len(b))
 	_, err = r.f.Seek(r.offset, io.SeekStart)
 	if err != nil {

From d59346c3a7eb4c2b49e9a2e7f706f05c9a0d694d Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:55:07 -0300
Subject: [PATCH 22/25] Revert "[desafio-07] *ReverseReader -> ReverseReader"

This reverts commit 41277925923c96fd10f17998cb50980444d4e1b8.
---
 desafio-07/MatMercer/go/tac.go | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index 2970c3f63..b8452f1ad 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -33,7 +33,7 @@ func NewReverseReader(f *os.File, size int64) *ReverseReader {
 	}
 }
 
-func (r ReverseReader) Read(b []byte) (n int, err error) {
+func (r *ReverseReader) Read(b []byte) (n int, err error) {
 	r.offset -= int64(len(b))
 	_, err = r.f.Seek(r.offset, io.SeekStart)
 	if err != nil {

From 135f5eb85942d45f4a2d8bf290e610880717fcb7 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:56:39 -0300
Subject: [PATCH 23/25] [desafio-07] Improve README.md

---
 desafio-07/MatMercer/go/README.md | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/desafio-07/MatMercer/go/README.md b/desafio-07/MatMercer/go/README.md
index ae71a4f39..3612413f4 100644
--- a/desafio-07/MatMercer/go/README.md
+++ b/desafio-07/MatMercer/go/README.md
@@ -12,6 +12,9 @@ md5sum out.txt
 Para testar os 512MB de memória com control groups v1:
 
 ```bash
+# install cgroup
+sudo apt-get install cgroup-tools
+
 # setup cgroup
 export CGROUP=osProgramadoresD7
 export CGROUPP="memory/$CGROUP"
@@ -20,7 +23,7 @@ echo 512M > "/sys/fs/cgroup/$CGROUPP/memory.limit_in_bytes"
 echo 0 > "/sys/fs/cgroup/$CGROUPP/memory.swappiness"
 
 # run in cgroup
-cgexec -g memory:osProgramadoresD7 ./tac 1GB.txt > out.txt
+cgexec -g memory:$CGROUP ./tac 1GB.txt > out.txt
 md5sum out.txt
 2b4fd25f11d75c285ec69ecac420bd07  out.txt
 

From 51edce4d8f001b7a5ca6802d0836f9adf0da7686 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:58:43 -0300
Subject: [PATCH 24/25] [desafio-07] b -> readBuf

---
 desafio-07/MatMercer/go/tac.go | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index b8452f1ad..cbc55e7cd 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -59,13 +59,13 @@ func tac(fileName string) error {
 	// buffers stdout by 128kb
 	stdout = bufio.NewWriterSize(os.Stdout, 128<<(10))
 
-	fs := fi.Size()
-	bufSize := min(fs, maxBufSize)
-	b := make([]byte, bufSize)
+	fileSize := fi.Size()
+	bufSize := min(fileSize, maxBufSize)
+	readBuf := make([]byte, bufSize)
 	maxRead := bufSize
-	start := fs
+	start := fileSize
 	lineAcc := bytes.NewBuffer([]byte{})
-	r := NewReverseReader(f, fs)
+	r := NewReverseReader(f, fileSize)
 	for start != 0 {
 		start -= bufSize
 		if start < 0 {
@@ -74,7 +74,7 @@ func tac(fileName string) error {
 			start = 0
 		}
 
-		_, err = r.Read(b[:maxRead])
+		_, err = r.Read(readBuf[:maxRead])
 		if err != nil {
 			return err
 		}
@@ -82,9 +82,9 @@ func tac(fileName string) error {
 		// search until backwards \n and prints it
 		lastEnd := maxRead
 		for i := maxRead - 1; i >= 0; i-- {
-			if b[i] == '\n' {
-				// write everything but '\n', since b[i] == '\n'
-				_, err = stdout.Write(b[i+1 : lastEnd])
+			if readBuf[i] == '\n' {
+				// write everything but '\n', since readBuf[i] == '\n'
+				_, err = stdout.Write(readBuf[i+1 : lastEnd])
 				if err != nil {
 					return err
 				}
@@ -102,7 +102,7 @@ func tac(fileName string) error {
 			// on last iteration, create a new accumulator with [max-read][current-accumulator]
 			if i == 0 {
 				newAcc := bytes.NewBuffer(nil)
-				_, err = newAcc.Write(b[i:lastEnd])
+				_, err = newAcc.Write(readBuf[i:lastEnd])
 				if err != nil {
 					return err
 				}

From e6de0bdd14cd80ad7e15d8705f700d1d76a3c464 Mon Sep 17 00:00:00 2001
From: MatMercer <contact@matbm.net>
Date: Sat, 12 Aug 2023 15:59:44 -0300
Subject: [PATCH 25/25] [desafio-07] Remove NewReverseReader

---
 desafio-07/MatMercer/go/tac.go | 9 +--------
 1 file changed, 1 insertion(+), 8 deletions(-)

diff --git a/desafio-07/MatMercer/go/tac.go b/desafio-07/MatMercer/go/tac.go
index cbc55e7cd..1b837ffb6 100644
--- a/desafio-07/MatMercer/go/tac.go
+++ b/desafio-07/MatMercer/go/tac.go
@@ -26,13 +26,6 @@ type ReverseReader struct {
 	offset int64
 }
 
-func NewReverseReader(f *os.File, size int64) *ReverseReader {
-	return &ReverseReader{
-		f,
-		size,
-	}
-}
-
 func (r *ReverseReader) Read(b []byte) (n int, err error) {
 	r.offset -= int64(len(b))
 	_, err = r.f.Seek(r.offset, io.SeekStart)
@@ -65,7 +58,7 @@ func tac(fileName string) error {
 	maxRead := bufSize
 	start := fileSize
 	lineAcc := bytes.NewBuffer([]byte{})
-	r := NewReverseReader(f, fileSize)
+	r := &ReverseReader{f, fileSize}
 	for start != 0 {
 		start -= bufSize
 		if start < 0 {